I've been in the same boat with older games, and using "Borderless Gaming" has worked well for me on Windows 11. It's quite compatible and actively maintained, so it's definitely worth a shot. Another alternative is "Windowed Borderless Gaming," which also offers similar functionality and has been around for a while.
As for settings within Windows 11, you might want to check out the Graphics settings under "System > Display." You can set particular games to use specific GPUs, which sometimes helps with performance. Also, using the "Compatibility" tab in the properties of the game’s executable to run it in compatibility mode for older versions of Windows may help with other issues.
Alt-tabbing is generally smoother with borderless windowed modes, but keeping your graphics drivers updated can also prevent a lot of headaches and performance hiccups. Let me know if you try these options and how they work for you!