You can definitely write to the windows file system from WSL, so long as you don't need admin privileges to do it. I use it at work and 99% of the files I edit are in a windows controlled drive.
For me, reading and writing works, but I have major performance issues on /mnt/. `git status` for example is unreasonably slow on any directory under /mnt/.
I tried to adapt to this by instead of writing to the Windows file system from Linux; to instead write to the Linux file system from Windows. After corrupting my profile 3x and having to reinstall WSL each time, I went back to vagrant[1].
When was the last time you tried? There are some file I/o improve EMTs over the past few months that drastically improved the kind of performance problem you are describing.
I tried to adapt to this by instead of writing to the Windows file system from Linux; to instead write to the Linux file system from Windows. After corrupting my profile 3x and having to reinstall WSL each time, I went back to vagrant[1].
[1] vagrant is also really slow on Windows.