See my response on best resolutions for the MacBook Pro at
And there is no behavioural change going to Sonoma 14.1 either. Yes, it is a RootsMagic 9 thing and not a Mac OS thing. This has been like this for well over half a year, even pre-Sonoma. I’m sorta-kinda happy that there is a current “fix”, but there needs to be a visible screen setting option in Settings for the Mac-side of RM9, which is lacking.