With respect to playing other storefront games, Proton is generally pretty good at handling them within Steam OS and worst case is you can dual boot Windows on the Steam Deck if you really need it. But if you’re really set on wanting to play the 2023 games on your handheld, the Ally Z1 Extreme is probably the way to go. The extra horsepower on the Ally really helps with poorly optimized PC games like Jedi Survivor and Starfield. The Steam Deck still does really well on new games so long as they are optimized well on the PC platform (like Cyberpunk), but unfortunately 2023 has had so many games with terrible PC ports, its difficult to really gauge how playable games will be on the Steam Deck in the coming years. The battery life is significantly worse but assuming that’s not a factor for you, the Ally may be the better choice.
I was trying out The Wolf Among Us yesterday on the Deck OLED and even though the game isn’t HDR the opening sequence had a lot of contrast and popping colors and it looked amazing with the perfect blacks on the oled.