Since you asked for matches, specifically, look at Denison U (small town with 10k population, Columbus is 30 minutes away), I’d add Smith (pretty vibrant interesting small city), and agree that Haverford/Bryn Mawr do seem to check off all the boxes for you though H is reachy for all.
Wesleyan -
https://catalog.wesleyan.edu/courses/comp/
“I’m looking for match schools that are preferably on the medium to small side in a suburban location, great math and CS departments, an undergraduate focus, and a quirky/nerdy student body. Most of the schools I’ve looked into have been reaches or safeties so far. Any suggestions?”
When I read this the first school that came to my mind is Cal Tech, it’s a reach of course and maybe you already have it on your list along with MIT and CMU. The LACs on the list are good suggestions and maybe consider RPI, WPI for additional matches.
@theloniusmonk Caltech was on my preliminary list, but I’ve eliminated it (along with MIT) because it’s an extreme reach and I’m not super keen on the STEM-intensive Core Curriculum (moreso for Caltech than MIT); although it might be slightly paradoxical since I have Harvey Mudd on my list: do you think these schools warrant a second look despite its crazy selectivity?
“I’ve been somewhat looking into UMichigan for some time now, but quite unsure about its size: I (personally) don’t think it’s worth it to pay similar tuition for introductory classes with hundreds of other students in a public school compared to smaller sections of lectures in a LAC/small to medium-sized university. Do you have any experiences/stories that you think might help me place how well I ‘fit in’ at UMich?”
Mathematics classes will never exceed 30 students, not just at Michigan but anywhere. Chances are, for intro-level classes, you will be taught by GSIs (PhD students), but once you hit the 200 level classes, you will have small classes taught exclusively by faculty. Since you are taking HL Mathematics at the IB, you will not be taking any intro-level classes in Mathematics at university, so you will start off immediately with Calculus 3 level classes, which are usually taught by professors. Michigan’s honors mathematics sequences (285-286, 295-296, 395-396) are arguably the best and most rigorous in the country.
CS classes tend to be larger as it is a very popular major, but Michigan’s placement in major Silicon Valley companies makes it worthwhile! 
With regards to other subjects (electives) you are looking into, I am not sure that intro-level classes at mid-sized universities are going to be appreciably smaller than at large public universities. An intro-level Econ or Psychology class is going to have hundreds of students in the lecture hall, regardless. It may be 200-300 at say Northwestern or Columbia vs 300-500 at Michigan, but you are still looking at huge classes. Once you get past intro-level classes, class size will vary on the popularity of the discipline, but typically, classes will not be much larger at Michigan than at a small private research university.
And by the way, Michigan does not charge similar tuition. It is cheaper than private universities, albeit by a small amount. All in (tuition plus room and board), Michigan costs roughly $10k/year less than its private peers. For example, Freshmen and Sophomores at Michigan pay roughly $48,000 in tuition and $11,000 in room and board expenses. Most of its private peers charge tuition rates over $52,000 and room and board expenses over $15k. So the difference is not significant, but it is not negligible either.
@CrewDad @OHMomof2 Smith has been on my radar, but not necessarily on the list as of right now simply because its a women’s college—I’m personally quite hesitant to go into an all-female environment, hence why both Wellesley and Smith aren’t super high on my list.
@Alexandre thanks for the insight on UMich! I like the sound of the cost (relatively better than any private school, I reckon) but I’m not sure my parents will justify the difference compared to a smaller, more traditional LAC-type college feel that I’d definitely prefer. I’ve heard amazing things about Michigan so far though, so I might look into it more if I have extra applications left (my school only allows each student to apply to 10 schools worldwide).
Interesting that you mentioned I won’t be taking intro-level math courses because of HL Math. I think having a school that values the IB is a cool added bonus, since it gets rid of the need for placement exams for credit. Do you know if any schools do something similar with Further Math? (I would reckon not, since there just isn’t enough people taking the subject for any one school to have a policy based off of it)
@theloniusmonk Caltech, although looking great theoretically (school culture + great math & cs department), doesn’t seem like the right fit for me. Hear me out: I love math and CS, and would not mind doing it the rest of my life, but I don’t share the same sentiment for the rest of STEM (specifically the natural sciences: chemistry & biology are my weak points). And Caltech/MIT’s notorious Core amplifies this—which honestly worries me.
The one exception is Harvey Mudd, which is high on the list, for a few reasons: HMC is a lot less selective than Caltech/MIT, the very deliberate undergrad focus (which is present at Caltech too, just not to the same extent), and the presence of the Claremont Colleges (also present at MIT w/ Harvard). Do you think these reasons are valid, or would you argue that Caltech and MIT warrant a second look?
Definitely go for fit. If you think a large university isn’t appropriate for you, Michigan definitely won’t do.
To be clear about IB credit, Michigan is not the only school that will grant you credit for HL Mathematics. Virtually all universities will. I know that Brown and Cornell do as well.
Speaking of Brown, I would definitely look them up. Their Mathematics and CS departments are excellent.
@Alexandre Yeah, my thoughts! Brown is already on the list, and my fingers are crossed for it (because a LOT of seniors end up at Brown from my school—about 10 every year). I’m just not sure I fit into the ‘hippie’ stereotype Brown is very commonly associated with, and the fact that ~50 kids apply to Brown every year.
Do you maybe have any suggestions for Brown-like schools that are less reachy and more of a match?
Brown is pretty unique. CMU and Rice are pretty good, LACish universities too, with slightly higher admit rates (15% for Rice and 22% for CMU) but they have palpably different settings. CMU has virtually no core, just like Brown.
Even slightly less selective than those would be Case Western Reserve, another LACish university.
Among LACs that I recommend for Mathematics:
Amherst College (no core either)
Bates College
Bowdoin College
Bryn Mawr College
Grinnell College
Oberlin College
Pomona College
Swarthmore College
Union College (that’ll probably be a safety for you)
Williams College
^Also, Carleton and Wesleyan!
If we’re talking about LACs in “match” territory with strong math programs, we ought to mention St. Olaf College, too.
https://wp.stolaf.edu/math/
The Princeton Review includes these liberal arts colleges in its sampling, “Great Schools for Mathematics Majors”:
Bowdoin
Bryn Mawr
Carleton
Grinnell
Hamilton
Harvey Mudd
Haverford
Macalester
Reed
St. Olaf
As much as I love the idea of Wesleyan and Swarthmore, they seem more like a reach than a match for me (unfortunately). If any of you are willing to help me review my full college list please send me a PM: I’d love to consult on my list as a whole instead of individual colleges themselves, but I’m not exactly comfortable posting my entire list online. @merc81 @circuitrider @tk21769 @Alexandre
Top LACs by alumni-earned PhDs in math/stats, 2006-2015:
70 Harvey Mudd College
42 St. Olaf College
40 Williams College
30 Carleton College
30 Swarthmore College
27 Pomona College
26 Oberlin College
25 Reed College
21 Whitman College
18 Amherst College, Haverford College, Wheaton College
Source: NSF/WebCASPAR
Of these, the ones that seem to be admission match schools are St. Olaf, Oberlin, Reed, Whitman, and Wheaton. Whitman arguably is in the “middle of relatively nowhere” (see above). St. Olaf and especially Wheaton have religious orientations that may be issues for some students. By this one metric, and also in light of the OP’s apparent preferences (for location, “quirky/nerdy”, etc.), Reed probably would be one of my top “match” candidates. However, the CS major there is new and the course offerings appear to be rather limited. St. O offers more merit money than some of the alternatives (like Reed, which offers none). If Minnesota winters and the Lutheran connection aren’t issues, St. Olaf might be worth a hard look. Oberlin, too.
@VaporeonKid, agree that Swarthmore is one of the toughest LAC’s to be accepted at as its acceptance rate, along with Bowdoin, is the lowest of the bunch. That said I think Wesleyan is definitely in your wheelhouse and it is also a great STEM choice.
Good luck!
@Chembiodad I agree: will definitely revise my list further and see if I have enough space for one extra reach to squeeze Swarthmore in.
Wheaton (if you are talking in MA) is in Norton, probably 40 miles from Boston, and more than an hours ride during rush hour either way. IMO, it is in the middle of nowhere. That being said, I know several students who attend there and they all seem to really like it. It is perfect for the suburban and south of Boston student who wants to remain close to home but have the real college experience.
Edited to add: I would also consider Wheaton a safety school or very low match.
@NEPatsGirl
Actually, I was referring above to the Wheaton College in Wheaton, Illinois. Not that either one is necessarily a great fit for the OP.