Let me keep this short for you.
I used to have an Nvidia GTX 980 TI, which could record at around 540fps CQP 30 in OBS at 1080p. Recently, I switched to an AMD Radeon RX 5600 XT as a friend of mine gave it to me as a hand-me-down gift of sorts. In gaming, sure, it's very good and much better than what I used to have. BUT! I encountered one problem, the encoder is much worse. I tried all sorts of optimization options, switching between H265 and H264, changing colour settings, messing with the bitrate, but it all lead me nowhere. In the end I could get by at recording in 240FPS with CBR 80K in 1080p or CBR 80K in 720p at 480FPS, a far cry from the 1080p540 my 980 TI could do. Not much meaning behind this post, really. Just, wanted to warn anyone about this as I couldn't find any similar posts on here.