I also was diagnosed in my (early) 30's. The medicine helps my mental health a lot. I feel so much calmer and my anxiety has improved significantly. I sleep much better when I'm taking my meds.
I notice an improvement in RPE if I lift or run while medicated. Not a huge difference in race times, but it helps me focus and not give up as easily. this was more pronounced when I first started taking my meds. I've been on them for over a year now.
However, I do notice a HUGE difference when I take it before work or engage in hobbies that are more mentally stimulating than running (pickleball, videogames).
I take two Adderall xr 10 MG pills daily. Since I started the medicine, I've successfully quit pot and caffeine use. I used to self-medicate myself heavily with those two substances before getting on Adderall.
My Heart Rate doesn't change much when I take my meds.