PLEASE READ THIS
I highly recommend downloading CryoUtilities, it will improve performance without losing battery life.
My graphics is always a balance between quality and performance, I don't like low graphics so trust me.

I also recommend DeckyLoader for adding plugins and EmuDeck for emulation.
The best plugins are:
- CSSLoader (Themes)
- ProtonDB/(to know real compatibility of the games)
- SteamGridDB (customize box art of the games)
- Bluetooth
- PauseGames (saves battery, pauses games in the background and when you put the Deck to sleep)
- ReshaDeck (Reshade in all games, I highly recommend adding LUT for better colors and CRT filters.)
- DeckSettings
- HLBT to Deck (How Long To Beat)
- AutoFlatpacks (Update apps from Gaming Mode)
- TabMaster (customize library tabs)
- Wine Cellar (Upgrade and install Proton GE, assume essential)
- MoonDeck (streaming from pc to Steam Deck)
- PlayTime (accumulates hours in non Steam games)
- AnimationChanger (change startup and sleep animation) and AudioLoader.

Try as much as possible to use FSR, it makes it look like 1080p, especially in blurry games like NieR. You need to lower the resolution of the game, unless it is 16:9 and fill the screen to remove the black borders.

Tip for Shooters lovers, I recommend playing with the trackpad instead of the stick, it's much more accurate and you can even activate gyro in all games, I recommend to follow this video and at least configure the trackpad and gyro, you can skip the rest if you like.
https://www.youtube.com/watch?v=iGHpetQb1BM

I recommend you to try lowering the Hz of the screen, for RPGs it is incredible, since you don't move the camera and the fluidity is maintained, my sweet spot will always be 40Hz or 45Hz in rpg games and 45Hz or 50Hz in games where you move the camera, if the Deck supports without problems I always try 60Hz, besides it increases the battery by lowering the Herzios.

I have a Steam Deck LCD so don't expect the same settings on the OLED Deck, the OLED TDP level is different than LCD. Low TDP in OLED will have worse performance than LCD while higher TDP will have better performance than LCD.