At launch, Steam Deck also had a lot of software issues.

I haven’t done such extensive tests, so somebody else probably can answer this better.

From my knowledge:

For minimum latency, you would want to disable all vsync (so ingame off and allow tearing), as well as the FPS cap. You could even overclock the screen (I believe the LCD goes up to slightly over 70 hz).

But this won’t necessarily be the best experience, because it will result in tearing, uneven frame pacing and increased battery drain.

For a more balanced experience, I found it to be good to have one vsync enabled (either ingame or via allow tearing off) and an appropriate FPS cap. I believe in theory, you don’t need the FPS cap if it is intended to be the same as the refresh rate and vsync is on (because vsync will sync frames to the screen anyway). But it hasn’t caused noticeable issues for me if I didn’t have double vsync.

What is the advantage of pre-loading the wallet? Getting a discount by purchasing Steam Wallet cards?

The issue is usually that both the in-game vsync, as well as the deck’s system level vsync is active. Therefore, it have multiple frames delay, which is very noticeable at 30 fps. Allowing tearing fixes this.