Yes exactly, the screen has an integrated UBS hub with 3 USB downstream for mouse, keyboard and so on and a USB upstream port which is then connected to the PC or notebook.
So office is no problem. I use the monitor regularly for team conferences or to broadcast intranet webinars.
I have not yet tested YouTube in full format or games.
No, unfortunately not.
The following monitors support PiP and PbP according to my information:
Dell U3818DW (38", 3840x1600)
LG 38UC99-W (38", 3840x1600)