As of right now, both models of the Go S listed on Lenovo's website have 32 GB of RAM (screenshotted below, if the weird screenshot functionality here works). So no, you're wrong here. The version with 16 GB is the Go 1. If there is a 16 gig SKU of the Go S, which there may be, they currently don't have it listed.

Memory size requirements depend on what you're trying to run. Easier to run stuff will run on everything, but from hands-on experience I assure you a bunch of newer games struggle with the default allocation of 4 gigs of VRAM and can use the extra RAM. You can still give 8 gigs to the GPU with 16 but then you're a lot more likely to start struggling with system RAM. If these AMD APUs worked like an Apple chip and could dynamically allocate RAM that wouldn't be such a pain, but at the moment you need a reboot to change this even on current-gen hardware, so it's easier to have a larger pool and give the GPU a little too much.

The amount of CUs and the VRAM aren't necessarily related. Even with larger RAM allocations and weaker GPUs you can find yourself in the wrong setup, which is annoying. And it's not just amount of RAM, these shared architectures can struggle with bandwidth as well, so speed can matter (although it's more giving you more or smoother FPS and the less the fall-off-a-cliff unplayable mess you get if the game is entirely out of RAM budget). That's also why I suspect being lighter on memory and perhaps having a better default setup may be a part of why SteamOS performance is disproportionally better on heavier scenarios compared to what you see on desktop PCs. I can't be sure, though.

This comes from me messing around with a literal handful of PC handhelds on Windows, SteamOS and Bazzite. I'm not guessing, I'm telling you what happened during hands-on testing.