Switch 2's new "Handheld Mode Boost" can run original Switch games at 1080p
The Nintendo Switch 2's backward-compatibility with Switch games is generally pretty good, and a few games have gotten patches from their developers to allow them to take advantage of the higher resolutions the console supports, among other features.
For unpatched Switch games running on the Switch 2 while it's docked, there should generally be no loss of quality compared to playing the same game on the Switch—the game will run at 1080p on both consoles and should generally run about the...