1080/60 all the way
I always have multiple monitors around, often times I'm recording/streaming and/or have multipe youtube videos running in the background at 1080p/60. Setting all these displays to 120 would negatively impact performance, without providing any real benefit sadly. Most games aren't even layed out for 120, much less all the other content you browse, so there's no point in going 120, as much as I'd love to. If I would dedicatedly only play a couple of games that support it (mainly talking about shooters) I'd definitely go 120 though, otherwise it's much more convenient to just stay at 60 for me.
Similiary, 4k isn't really worth it for me personally. Ignorance is bliss I guess. Metaphor Refantazio is a notable exception to that, because it looked like shit on 1080 for me, so I actually needed supersampling to fix that.