You are correct that a reboot will trigger a full rescan. I’m always on the lookout for better sync. I just don’t think it’s out there right now for easy bidirectional sync.

Basically, if you want to set and forget, Syncthing is the best option. If you want more control, you’ll need to look into setting up rsync scripts or similar, which will at least better let you control how often to sync.

In theory I guess it provides better security in some ways, but certainly not all over giving you hardware and a VPN. So there’s that. But yeah, it sucks.

I don’t know what your particular situation is but if you’re just using it on computers you could use LUKS or BitLocker or FileVault. Then if you want to wipe it, you only need to destroy the key and the data is rendered effectively gone.