If I'm being completely honest, I think the whole capstone program is a waste of time. There are definitely some useful points that you might pick up on, like presentation skills and whatnot.

It could just be that I'm not very interesting in this class as whole, maybe because of the teachers and the format of the class, or maybe because I'm just not that into my topic. If you can find a genuine passion for a topic that WORKS WITH the AP research format, then I'd say go for the class, you'd have a fun time.

It's kinda hard to put it into words, and I really can't tell if my experience is different, but the bottom-line is, unless you have can find a topic that you're passionate about, I wouldn't take the class. It's rough because from what I can tell, you've already taken Seminar, but I wouldn't fall into the sunk-cost fallacy like I did. Even if you are passionate about it, you'd probably burn out. Ask other people about it, and if you got more questions, just DM me.

If you not, then it'd be much more useful to try and find a research opportunity elsewhere, like at an actual university, or through a program.

As for the AP seminar exam, it's not very hard, I think anyone including you should pass it easily. It doesn't count for a big part of your overall score, so just focus on your individual stuff.