Can attest that Folder Sync is excellent. I use it all day (in the background) for two-way sync (notes) and backup of photos videos etc

Though a small PSA on setting up:
I once set up a new share on a new phone with two-way sync, and the app decided to sync the (newer) empty directory to the server (i.e. delete everything) instead of pulling the files from the server to the phone.
Easy fix: Restore notes from backup (step 0: have backups in the first place), then do an initial 1-way sync from server to phone, then change the sync job to two-way.