I have syncthing and syncthing-inotify installed and use systemd.
As the syncthing service pulls in the inotify service, it looks to me that, unless I do a bit of fiddling, if I were to enable the built-in fswatcher, I would be watching all folders twice.
This doesn’t seem to be useful, so I haven’t tried it.
BUT, does either or both the internal and external watcher recognise the other with one deferring to the other? If not, this might be useful to ease the transition.