Understanding work-spaces on macOS - Why does it not save Applications and Positions
There has never been any provision in Spaces for one app to be on more than one Space. It's simply outside the design spec.
You can pin an app to a Space but you cannot pin a window to a Space. Quit &amp; relaunch &amp; the windows will all fold into the same Space.
Window sizes should be remembered, but not if they wouldn't fit the display they opened on.
Sleeping the Mac should work, but will be dependant on whether the external display stays 'visible' to the Mac at wake. On Mac Pros here, desktops with multiple external displays, this works just fine. idk how well laptops handle this. Sometimes forcing the display to wake before the Mac succeeds in maintaining the connection.
One additional point - Macs don't really need shutting down or restarting all that frequently. Mine generally get rebooted for OS updates etc, the rest of the time they are awake or asleep. Maybe once a month or so, if I feel things might be getting a little sluggish, I will reboot. I've had Mac that ran a decade with little more than this. One never even slept, it was up 24/7/365 for 10 years with the occasional reboot for updates or a shutdown twice a year for a good clean.