Running very similar spec. here but with more RAM and 2080Ti card. Mostly ultra settings and running an ultrawide (3440 x 1440) monitor. Normally 45-55fps in open country at low level, dropping to around 30fps in urban/busy airports. I tend to fly everywhere at around 100 feet AGL, not interested in high altitude stuff where frames rate improve (usually).
So at 4K you should be OK for useable FPS. If you can afford/configure it, do consider 32GB RAM. My system uses between 22-24GB while flying.