A method i'm using, for example in Axiom Verge is ahk script just before start the game.
...
Sleep 5000
WinGet, OutputVar, PID , A
WinMove,A,, x1, y1, x2, y3 --> this function selects desired window or crop
Sleep 500
run, "c:\users\arcade\utils\dc\sr2\switchres.exe" %x% %y% %v% -f %x%x%y%@%v% -s -k -i "c:\users\arcade\utils\dc\sr2\switchresK.ini" ,,Hide, OutputVarPID --> change to 240p
exitapp