SteamDeckHQ which has Steam Deck settings as well.
Show Great on Deck as a Browser extension (Firefox/Chrome) which displays ProtonDB and SteamDeckHQ on the Steam Store and links directly to the correct subpages.
Games can do that and some do, but mostly they run like on any other PC with their default settings, or sometimes they try to guess the initial settings based on the hardware spec (like texture quality based on amount of VRAM)