I’ve set up syncthing on both my workstations to sync certain folders. Because the devices are rarely online at the same time, I have a VPS with syncthing in the middle which both devices sync with, something like this:
I have 2 central nodes (local+remote) which connect all my other devices. Over the past year it worked reliable enough that I would call it almost stable. The main folders are encrypted and conflicts are rare. What happens more frequently are stale items like 0 byte files which can be annoying but are easy to fix in most cases.
With only 3 devices, however, this should not be a big problem. What are your main sync issues?