Hi,
I am using DT on my Mac and iPhone and so far using Bonjour to sync. My databases are all stored locally with nothing in iCloud.
My question is that if I use iCloud (CloudKit) to sync, will that eat up the storage in my iCloud in proportion to the size of the synced databases? I have some huge databases and don’t want to use up my iCloud storage that much.
TIA for your help.
Yes, it will. Not the same size but nearby.
My question is why this question? 
Syncing with Bonjour is direct; device app<>device app
Syncing with iCloud(CloudKit) uses an intermediate sync datastore;
device app<>sync datastore<>device app
The sync datastore is stored in the cloud; adding to our cloud storage
(in proportion to the size of the synced databases)
We can be selective as to which databases are sync’d
For me, the benefit of cloud sync is the Devonthink app does not have to be active on both devices at the same time
I use iCloud(Cloudkit) sync, with Bonjour as backup
True but there are other options, depending on the device and situational needs, e.g., WebDAV.
Ok. So it’s better not to sync huge databases with the iCloud option when cloud storage is limited. Such database can be synced via Bonjour while other databases can be synced via icloud.
I’m new to DT and still exploring my way. Bonjour is great but limited by my location/ network and real time sync via other options might be better for certain use cases.
But thanks anyway. It’s always useful to give a second hard look at the question.