Played around with getting the emulator for Baku Baku animal 'perfect'. It runs fine, but just windowed, controller setup is a bit off to compared to the simple and effective way you do it on a 'proper' pc with a 'proper' USB controller. Basically I could register the important buttons (the game only really needs the D pad and one button or two to rotate blocks a la Tetris). Biggest downer was the issue with Windows updates - it seems that the updates that need a restart halfway are problematic. Restarting (via this soft reset/ restart) goes to Steam OS, and if you the reboot in Windows, Update has kittens and says it has to undo the changes. Maybe there's a work around as there are only a few reports on this (with no solution).
With this, I tried the Retroarch based Saturn emulator on Batocera. Didn't work (went to menu, disk not detected), then played around with Bios (adding more than usually needed on PC) and then voila. Full screen full speed Baku Baku animal.
I'm happy, but am now reassessing my use case for this machine. If Retroarch Saturn emulation works, I can just use Retroarch on Steam OS. if so, then I don't need Batocera (which is basically booting into a new OS on microSD). It's not that inconvenient, but I would need to upgrade the 64GB SSD. I was waiting for the Sabrent 1TB which is back ordered until end of the month. Or I could go for a 512 now. Probably best to wait. And so far, I don't really need that much room on the internal drive at the moment as I have only installed the last 'long' game that I played through - Brutal legends which is 8G.
If I can't overcome the windows update problem then it's probably not that good as a secondary 'work' machine when travelling. It's not that bad in any case, as bringing a steam deck with a portable monitor (and keyboard/ mouse) isn't that much lighter than a steam deck and a (nongaming) laptop. LOL so much to think about.
Overall, I'm impressed mostly.