NVENC Encoding Queation

Apologies if this has been covered before, but I can’t find any sort of information I feel 100% confident about. I have a few high end GPU’s I would like to start benchmarking and recording to post on YouTube. Nothing crazy, just playing the games, seeing the performance and helping people make informed decisions about what resolution/settings/games performance they can expect.

That said I plan to use my main benchmarking rig, and a second PC to handle the recordings through OBS or Meld Studio (not sure if that matters for my question). The second PC has 32GB of DDR5 RAM and a 14700K. It’s no slouch, but currently I do not have a GPU installed.

What would be the cheapest GPU I can buy to do what I need to do?

Are all NVENC chips the same or does the 30 series perform better than the 20 series? If it does, would it matter?

Can the 14700k just handle it? Would having a dedicated NVENC GPU make a big difference?

Planning on capturing at 4K 60 fps. Thanks for the assistance!