HR and exertion tracking recommendations?

I just got diagnosed with POTS, minor WPW, and hyper-mobile EDS. After years of thinking everyone lived the way I do, I finally am trying to track symptoms and make changes to improve my functioning. Wondering g what recommendations people have for devices/apps/things to do to track heart rate and related symptoms.

I currently have an Apple watch series 9, and it’s great in many ways, but I find that the HR sensor often is quite slow in giving a reading. I’ll start to feel my heart race, or start getting dizzy, and go to check my HR, but sometimes it won’t give me a reading until I can already feel my heart stabilizing.

I briefly used a Garmin and remember it having faster HR responsiveness, and I really liked the “body battery” feature since I struggle a lot with accidentally overdoing it and paying for that for days. But I don’t want to consume or invest in a new device if it isn’t going to pretty dramatically improve something.

So, what do yall use and what recommendations do you have?