Will be any performance change between 4k and full HD monitor?

Hey! I quite a long time working in ue5 with 1920x1080 monitor. I want to buy 2k or even 4k monitor. My question is simple: Will be any performance drop after changing the monitor because of increasing resolution (for example in games it is and very huge)?
I have 3090 ti and in some projects Im going with it till 20 fps - so I just cant make my fps even lower.

Also 1 more question - if I will buy second monitor (both will be 1920x1080) and open on them both ue5 somehow or just another program - will I got fps drop also?