Question about LG 32ud99-W

Yes, this monitor can display the picture from two inputs side by side at the same time. There are not many settings for this function - one input for the left side, one input for the right side (or of course one input for the whole screen). You can stretch the image vertically or keep the aspect ratio (and leave part of the screen blank).

(I have this monitor at home).

@Pescheli
Maybe another LG monitor makes more sense for you (if you want to display 2 or more sources at the same time).
Otherwise, as Brimstone has already written, with most monitors you can switch between sources simply by pressing a button.

- Quad PBP (picture next to picture)
http://www.lg.com/de...
LG 43UD79-B (43", 3840x2160)

What do you mean? At the same time?