Thanks for that advice, yeah I did install openbox, but not lightdm, I did already set up an autologon pre-x, so I just use xinit to start openbox, this works nice.
Now I just need to configure some things in openbox, for instance runcommand and retropie-setup scripts run in a very small window in the center of the screen (I have a 4K screen), I guess I need to force fullscreen for everything, set larger font un xterm and/or set higher dpi at the openbox level.
But Redream and PCSX2 run full screen so I'm almost done, I'll try to add more stuff like xemu, kodi and whatever I can now that there is an x server, this actually makes everything a lot easier... My mistake.