Well actually it's not the files in the desktop issue but I connect to a NAS at startup and open the finder windows accordingly. The prob is, one mac has a smaller resolution than the other, so on each system start these windows are misplaced. To make it a bit more clear:
Mac A has a 32" 4K screen connected, Mac B has a 2k resolution.
Last time I run Mac B, I organized its desktop to the 2k resolution and shut it down.
If I start Mac A first and organize my desktop accordingly to the big screen and launch the Mac B after - the desktop on mac B is a mess. So I tidy up the 2k desktop again and again.
Fun fact. If I shut Mac A before Mac B down and start Mac A up, the desktop on mac A is a mess 😀 😀. It looks like the Desktop of Mac B with some more overlapping windows.
My conclusion - these macs try to sync the desktop and fail each time, regardless how I organize the desktops. Btw. I had not the problem with Mac A before I connected the Mac B to the network.