How likely am I to get into University of Edinburgh or UCL?

I am currently a student in the US trying to get into a university in the UK.

I have a unweighed GPA of 3.93 and a weighed GPA of roughly 4.25-4.3.
I took AP World History last year and got a 5 and am taking AP Bio, AP Calc AB, and AP Lang and am predicting a 5 in all those subjects as well. Next year I plan to take AP Chem and AP Physics (+3 other insignificant ones).

I want to study molecular biology/ neurobiology which I appear to be quite competitive.

I have a lower SAT score of 1340 as well.

As far as extracurriculars I have a few for pretty much any area you could think of from sports (Varisty + awards), ASB, Club President (TedEd), Orchestra (varsity), and many more. I am a three time national competitor for TSA and was a semifinalist last year. I also have roughly 500 hours of volunteer work as well.

I was hoping to see the opinions on others on my chances of acceptance. Any comments would be greatly appreciated!

Admission for international students seems to be pretty straightforward. If you meet their admissions requirements (which I think is a certain score on the SAT or ACT, plus 3 relevant AP tests with score 5, or can use SATII tests as well), then you’ll get in. You will apply on the basis of your scores for AP Bio, AP Calc, and AP Chem or Physics. To be sure, you should take the SAT subject tests in bio, math (forget which one), and chem and physics. There is an essay, which should very clearly state why you are qualified and motivated to study neurobiology/molecular biology. The scores on the non-science AP tests won’t matter. They don’t really care about GPA and general extracurriculars. You apply via the UCAS application, or you might be able to apply via the common app as well.

Calc BC would be better than AB, but with bio, chem and physics you should be OK. You will want to be getting 4s and 5s on these, with at least one 5. That should get you an offer from Edinburgh. For UCL you’ll need to raise your SAT a bit and get 5s in all the STEM APs you’re doing. In either case the offer will be conditional on the senior year AP scores (I presume you’re currently a junior).
Your GPA doesn’t matter per se, but you will need a strong rec from, preferably, your bio teacher.
ECs don’t matter unless they’re related to bio.