I thought about this issue a long time ago but never posted a request.
My Axon 7 is a multibooter with several ROMs. It has an SD card where I keep music and videos. I installed /e/ 0.1 on it. Later I got the /e/ account and added storage space. Later I installed /e/ on the Essential PH1 mata which has no SD card. Copied all my music and vids to it. That stuff synced to ecloud which later synced back to the Axon which then caused me to run low on internal storage (not to memtion the redundancy). I turned off the syncing of Photos and Videos and deleted the files. It was awhile before I realized no documemts were syncing.
Fast forward to “today”, the Teracube has replaced the Axon. It also has an SD card where the multimedia files live thus the same situation again. I need Documents synced but not the other stuff.
I sync documents from the PC desktop via the Nextcloud client but they don’t get synced to the Teracube since Photos and Videos is toggled off.
The Nextcloud mobile client does not have/do proper 2-way sync. There’s a thread about that in the NC forums. Folks recommend all kinds of sync methods (like syncthing) but as one person put it, you need a client that fully supports Nextcloud/ownCloud cataloging. This way deletions, modifications, etc. are properly handled.
AutoSync by Metactrl(?) is the best bet (tried it and it works great) but it is trialware and can only be paid or subscribed via Google Play.
FolderSync (Pro), which was already on another device to sync some office docs to ecloud, was the next best solution. I now use that to sync the Teracube’s Documents to/from ecloud. I’d rather not use a third-party sync app though.
If nothing else I think Documents should be on a separate sync channel. So yeah, they should all be separate IMO (Documents, Photos/DCIM, Music, Videos/Movies, Pictures).
Side Note: FolderSync Pro is one of those apps you can buy directly from the developer.