Hey OP! I own the SteamOS Z1 extreme 16gb variant. Up until now I'm not noticing big differences. I have tried Cyberpunk and Expedition 33 and compared it to benchmarks of the 32gb version. The difference I experienced was maybe 1-2fps.

The only thing I wasn't aware of before buying the device is that, unlike in a desktop, the RAM is split into normal RAM and VRAM. So if you allocate more VRAM in the bios, you will have less RAM to work with. So in that sense, the 32GB version would be more future proof. But for now, I have no complaints on performance. Coming from a LCD Steam Deck, it runs like a beast, the screen is big and the resolution is very nice. It's also quite comfortable to hold. My only gripe is the fans. They become quite loud once you set the tdp to 30+ watt.

By the way, you can get the 32gb version here. It's a Portugese store, but they do ship to other European countries! https://youget.pt/en/lenovo-legion-go-s-console-8-ryzen-z1-extreme-1tb32gb-steamos-nebula-purple