They continue to be great on newer GPUs, although the first ~6-12 months might have some small bugs. I have really enjoyed my RX 7800 XT. It’s working perfectly now, but I had an issue specific to newer GPUs where every other boot would fail (Arch Linux). It was a known issue and fixed in kernel 6.7.3 (I think) and issues like that seem to be rare.

Nitro is just a marketing term for their high end models, they usually have the Pulse which is the base and the Nitro(+) that has additional features like removable fans.

They cost more but they tend to have a better build quality, but the chip inside is the same.

I got a Radeon 7800XT in March and have had no significant issues with it on Arch Linux. The issues I have had were from running the bleeding-edge mesa-tkg-git drivers which are the pre-release development builds, and sometimes things break there (I had a weird issue where red and green got swapped in X11 apps). You have to go out of your way to run those drivers though, stick with the released version in your distro’s repository and you’ll be fine. I can play most games above 100Hz at decent resolution and quality. I have a 4K 144Hz monitor with Freesync but for more demanding games usually need to turn down settings a bit or use resolution upscaling like FSR. I upgraded from an Intel Arc A770 and it was a big performance increase.