It does. It's configurable on a per-sync-folder basis.

Not sure why you'd use nextcloid over ST for just sync. ST takes 5 minutes to setup.

I also recommend for:

Windows - SyncTrayzor

iOS - Möbius (costs like $10, but can do background sync)

Android - Syncthing-Fork, it moves most of the sync conditions to within each sync folder/job, for more granular control.

Nice thing about ST is its not server-based. It's machine to machine. That is, you don't setup a server first, you just install ST and send your device id to another machine and they connect.

I keep hundreds of gigs synced between several computers and several phones. It's become pretty messy, because I was lazy.

But it rarely has an issue, and it's pretty good at telling you what the issue is. The desktop version is a little easier to handle errors than mobile, but that's mostly because mobile client is simpler.

But within the mobile client there's an option to switch to the web client view which is much more detailed. I only have to use that once or twice a year, and usually because I've done something like reset a phone so a share doesn't see that phone anymore and is confused.