I recently purchased the Benq SW 320. It is a 32 inch 4k monitor. Screen is really nice and I very much like the features. The problem I am having is the following and not exactly sure what to do about it.

Many sites and photos look amazing on it. It seems to make what were already really nice photos into just perfect photos. Sharpness and colors are just great. But many other photos look bad. For instance just about every photo posted to BPN does not look good on the monitor. When I check them on my phone or other devices they look good. So not sure if this is a 4k issue. If maybe the 1200 x 800 photos are just too small when viewed on a 32" monitor or what? When I view my photos in PS they look great as well but the issue seems to be with web based photos that are not high resolution. Anyone else experience this? I don't think it is an issue related to the monitor as photos on Arash's site just look outstanding. Wondering if others have had this issue and what you do about it. Any and all help would be greatly appreciated. I am still in the timeframe where i can return the monitor if I decide to do so.

Second issue. For those that have 4k monitors, do you leave it in Adobe RBG, process in RBG or in SRBG?