@ChemTeachGuy I personally am using Princeton Review. From what I've heard and what I know from experience, TPR provides and emphasizes lots of details. Some pre-meds think that TPR is for the person who doesn't have in-depth science knowledge, are career changers, few years removed non-trad, etc. With that, the notion is that Kaplan is for the opposite type of person.
I'm using TPR's self-prep and I think that their bookset overprepares you. Their practice exams are also much harder than AAMC. If you were to ask me 2 weeks ago to recommend TPR, I would've said no. But that was because every practice exam I took with them was consistently low. This week I just took AAMC FL2 (509) and jumped 9 points from AAMC FL1 (500). In between those 2 tests, I took 6 TPR exams. All within 498-505.
I think that you couldn't go wrong with the TPR bookset. It hammers details, but you'll see results in the end.
Lol and to answer your other question: Buy a bookset, not per subject.
I felt very comfortable with psych/soc concepts, but wasn't scoring that well on that section on practice exams. You may think you're strong in something, but it never hurts to read another book for review -- especially in your case where you've been an alumnus for a few years.
Good luck in your prep! I hope my advice helped you in some way or another. Also, if you're interested, I'm trying to get rid of a new 2020 TPR bookset that I received when I joined their online course. I had already paid for one months before I signed up for the course, not knowing the course provided you with one. Let me know!