That sounds... slow. How is it working out?

There were a lot of problems getting proton to work on NTFS, but that's only because the COMPATDATA directory must not be located on NTFS. Worked fine the moment you symlinked COMPATDATA to your ext4 drive.

There was a time, where this problem got discussed almost weekly on reddit.

The problem is that the way NTFS works will not allow you to do symlinks and there are some permissions issues.

There are some workarounds but these might still cause issues.

That mainlined ntfs driver is fast but occasionally drilles holes in ntfs so I have to chkdsk on Windows. Also NTFS is not mount & play, you need to configure it with right permissions etc.

My experience with hasn't been good, as it failed to read some files properly, while ntfs-3g can read them just fine.

Windows users don't need to worry about Wine/Proton

Winbtrfs has some really funky bugs (some apps like Aseprite will somehow make files which get padded up to a round KiB size on disk which breaks some file formats, even though it doesn't do that on NTFS or FAT), is way slower on Windows (longer loading times, streaming asset delay, delayed audio on some situations like RPG dialogue, Skyrim mods are especially problematic, blah blah blah), the extra permissions make managing it annoying, and symlimks generally just don't work on both Linux and Windows at the same time no matter the FS which can occasionally be annoying. I really wouldn't bother with winbtrfs for games unfortunately

That's the NTFS3 driver for you. Corrupter of partitions... I had so many hassles, and it's still happening to others recently, I don't know why that thing is included honestly.

I was doing the same with winbtrfs, and it's pretty good overall but kind of a mixed bag sometimes. The biggest pain is file permissions since winbtrfs isn't sane and use something like uid 1000. So when you write or alter files or you'll get file permissions errors on the Linux side. It's workable just changing the permissions back when in Linux if that happens

when the ntfs3 driver was released I moved my games to an NTFS partition, i don't remember precisely but some wouldn't work, and then unlike my ext4 or btrfs partition which were unbreakable, a lot of things became unreadable and undeletable after a forced shutdown

Did you symlink the compatdata folder?

now I'm planning on making a btrfs partition for my games and using winbtrfs

I heard that with winbtrfs, you run into permission issues where every time you boot back into Linux, you'd need to chown any files you'd created in Windows, which would be a PITA. Also, I heard winbtrfs in Windows isn't as stable as ntfs3 in Linux. Neither solution is unfortunately perfect so you may need to try and see what works best for you.

In general though, I believe regardless of what filesystem you choose, it's recommend to NOT share everything and instead maintain a copy of the library native to each OS, and just share the "common" and maybe the "download" folder, and let Steam discover the existing files when you proceed to install the game.