1. With DLSS 2.0 you can get 120+ fps in a lot of things on the 3080 @ 4k

2. No one need do anything except die, but shaving a few ms of response time is nice for productivity. No one thing is critical but making sure you have a keyboard, mouse, monitor, refresh rate, and programs that aren't throwing latency out the window makes for an overall nice feeling system.

My understanding is that if you aren't gaming (i.e. most of the content on your screen is static) your GPU is smart enough not to redraw the entire frame so you can probably get very low latency refreshes.

Even without DLSS, this isn’t necessarily true. My 3080 has no problems pegging some recent games at 144-160 fps at the corresponding refresh rate. In fact, I’m generally CPU bottlenecked at 1440p or below.