720p upscaled to 1080 looks really good, and is a nice balance for performance.

Some TV don't play nice with the fps caps, try uncapping the framerate if you don't mind some fps fluctuations.

Rock&Stone btw.

This is just my personal settings I've found that work well for playing on a TV, but I usually cap my fps at 30, limit my external display resolution to 1920x1080 (you can set this for all games in SteamOS settings) and enable FSR. Goal is to still run the games at 1280x720, but use the FSR to upscale to 1920x1080.

I cap the external resolution because there is a noticable performance hit when using FSR or similar tech to upscale to 4k.

Ideally you'll adjust both in game settings and deck settings for each game with in-game settings taking precedence as they give you access to fine tuning custom tailored to that game. The deck settings are great to tinker with when you want longer battery life especially. If it's inside the dock and charging while you play you needn't worry much about optimization (frame rate limit, heat limit, half rate shading, etc.) and can leave it at the sensible defaults.

The Steam Deck per-game control layout is very helpful for games that don't come with native controller support or those that don't let you rebind controls inside the game itself.

I don't own the games you mention, so I can't suggest specifics but my general way of setting up a game is:

1. install the game and get it running at all
2. use in-game options to find a resolution and layout comfortable from your preferred playing posture/position
3. enable frame rate overlay in the steam settings
4. start with default or auto detect settings for graphics or look up what others recommend online in sites like protondb. if you hit a comfortable frame rate (40-60+ for me personally) keep increasing the graphics quality settings in game as long it remains fluid to play. Don't need to do it all in one session. I usually minimally increment the graphics settings at the start of each gaming session and simply revert once it's no longer fluid.