Being an introvert doesn’t equal shy, so I assume when you look at smaller schools, as opposed to state universities, you don’t have a problem speaking up in class. D1 went to small, highly rated LAC and D2 to honor college at big U that means she has smaller classes, but for both of these grades are pretty dependent on participation. D1’s school had spring term where most classes had group projects.
I think an introvert can do well and enjoy any school. D1 is definitely one but mostly in terms of needing her own down time (outgoing in classroom situations). Having her own room helped, plus finding ‘timeout’ spaces on campus, such as the piano rehearsal rooms. Piano was also a stress reliever.
IMO you have to take into account whole experience - may want to look at large schools with honors programs. In D2’s program even intro classes are smaller (she had 1 75+ class in 4 years, most 30 or less, many 15 or less). But you have option of including a few larger classes where you can disappear. Look for schools with options of single rooms or ability to have year-long assigned study cube. Look for schools with solitary activity options, like good places to run or practice instrument, etc.
You said you’re not party guy but what would you do in spare time? Do you want films, speakers series, etc that are not participatory? Again, not sure these should be deal breakers. Do some visits and attend some classes. Don’t use your HS experience as measuring stick for college. Visit a small class and see if you like the level of interaction. Visits will help you develop a better sense of must haves.