Syncthing is great (I use it daily!) but I'm not sure it does the Dropbox/NextCloud thing that BTFS does where you can see remote files and download them on access. Syncthing rather just syncs folders as far as I can tell.

Syncthing experience is greatly improved if you also host your own discovery server, and if you can port forward.

Pretty minor to do, but, it's a big speed increase.