Resident Evil 2 installed...not on the supported list and runs perfectly! Few tweaks on the settings and you're set for 60fps locked. However if battery life is what you're after then slap the 30fps cap on and the estimation looks great.
Elden Ring - High for most settings, 15w max power selected, 30FPS lock on Battery approx. 2-2.5hrs
Resident Evil 2 - High for most settings, 15w max power selected, 30FPS lock on Battery approx. 3.5-4hrs
This demonstrates how much time you're going to get out of the battery depending on the game stressing the GPU. If you raise the FPS cap to 60 for RE2 you'd be looking at a similar time on battery as Elden Ring.
I'm really impressed so far with the Steam Deck, played around an hour on Elden Ring, took on a dungeon boss, started to progress up the beginning path and it was great to play on. I'll need to dial in some additional settings as it became bogged down (25fps) in very frantic fights with multiple enemies/spirits called in but great first impression. FSR doesn't really work properly yet for it however as you need to lower the res, when you do so it doesn't scale to the screen so that's annoying. Didn't try FSR on RE2 as it didn't need it.