I will do some research to see if any compositors like that exist.

The refresh rates of each input get limited when using the picture in picture modes though. But if there exists any external hdmi/display-port compositors that support 240hz and allow arbitrarily sizing/placing the inputs than it could work as this monitor supports 240hz + gsync/freesync

The Samsung 57"/49" Odyssey Neo/Oled G9 can almost do what your looking for but it can't do the smaller aspect ratio of the monitor wings, which is annoying because it probably could do it in firmware if samsung had implemented it.

A