Remote access resolution and screensaver issues
I'm a Mac newbie, with Windows and Linux experience, running a new Mac Mini M1 with Big Sur 11.1, having various issues with VNC access.
When the physical 4K monitor is disconnected from the Mini, the client window shrinks to 1920x1080. About -> Displays shows an 'unknown display' 1920x1080. No other resolution setting is available. I installed EasyRes, but it also doesn't show any other settings. My present workaround is running an HDMI cable to an unused input on a 4K monitor. A dummy display HDMI dongle would likely also work, but I'd prefer a software solution. How can I find the config file that defines the 'default' display (gets used when no hardware display is connected)? Is it safe to edit?
When the remote connection is active, the screensaver would start up after 10 minutes of inactivity, even though in System Preferences -> Desktop & Screensaver, Start After is set to Never. Also, in Energy Saver, Turn display off after is set to Never, with Prevent computer from sleeping ... checked. A search suggested disabling fast user switching, which helped, but the screen saver still comes up after a few hours. Once this happens, control from VNC is lost. Keystrokes or mouse clicks don't stop the screensaver, nor does putting the cursor in a Hot Corner set to disable it. Disconnecting and reconnecting, which correctly brings up the login screen doesn't help; after login the screensaver gets immediately displayed again. Even selecting Restart from the login screen doesn't kill it. I can log in via ssh and reboot to regain control, but this obviously results in lost work.
Finally, I'd like to log into a virtual display, concurrent with a user on the physical display. There are various articles explaining how to do it, but they imply that the two sessions must use different user accounts. Is there a way around this? If not, is there a way to be logged in remotely as user A but be able to access and modify user B's files, without permission issues, while user B is logged in on the physical display?
Thanks in advance for any guidance on these issues.
Mac mini, macOS 11.1