Steam deck - steamOS AND Windows 11

Sharing games between OS's can be done, but from what I understand it's awfully unreliable. Even at a low level you've got to use a format that both can use (BTRFS is commonly quoted).

Have a think about why you'd want to have them accessible by both Windows and SteamOS. At the very least format the SD card to BTRFS so they can share the storage but don't try and share the games. At least then you can have Windows games in one part of the card and Steam games in another.

And give SteamOS a chance, don't switch straight to Windows. I hated it, it lasted maybe two days before I switched back. The drivers are just written to 'get you going' rather than being regularly updated, and I find Windows on a handheld is 'clunky'.

If you're on Facebook I'd suggest joining the group 'SteamDeck Tips Tricks Hacks & Emulation', there's lots of very knowledgeable people on there. (edited)

The general consensus is don't run Windows from an SD card as the constant read/write will prematurely kill the card. I upgraded the M2 and then partitioned it to run Windows 11 so I could use my Gamepass Ultimate sub with it.

As above, if you have a big enough on-board storage, partition that instead (min. 256GB).

My setup is a 1TB on-board NVME, partitioned 250GB SteamOS, 750GB Windows, and 1TB MicroSD card formatted as NTFS. There were a few commands needed to get SteamOS to see the NTFS card but once done it works fine. I do install Steam games on the MicroSD and it is possible to play them on both SteamOS and Windows, only gripe is that there is a few minutes install when you fire up a game on the other OS for the first time. I mainly use the SD Card to store and run ROMs and games from Jack Sparrow.

I thought I would use the Windows OS more, but I do find myself drifting back to SteamOS where possible and using the Windows OS mainly for Game Pass games - SteamOS is just easier to use, better on-the-fly performance overlay, better battery and better game suspend options. I'm happy with my 75/25 NVME split as I have plenty of space for Game Pass installs and enough to run SteamOS comfortably, especially utilising the MicroSD across both OS's.

Probably better off posting in the steam deck Reddit forum or similar.