The WSL filesystem is already exposed at \\wsl$\distro-name (that landed in the Windows build from 6 or 12 months ago, so you can try it now on a release channel WSL 1 distro). I doubt that’s enough for file watching (certainly things like file locking aren’t supported), and I don’t believe CIFS would allow that either.

For watching file changes specifically, I imagine that you’d need a helper that could run on the Linux side and do any inotify or similar stuff there. I have no idea what IntelliJ might or might not support along these lines. I get the impression that VS Code is generally the tool with the best support, though again I have no concrete knowledge about file watching in particular.