For now, I just want to create a database, store that database on the OneDrive folder on my Mac, and use it on one machine. For now, I will not sync that database to iCloud or any other cloud service. Will that be a problem?
Nothing has changed in cloud in this regard. You should never put DEVONthink databases in any cloud-synced location or you could irreparably damage them. To this end, DEVONthink disallows creating, opening, or syncing a database in such a location and issues a warning about it.
In the future, I may want to index folders on OneDrive.
If maintaining tags on the documents isn’t important, then yes, it’s feasible. See…
I suspect if I decide to sync between machines, I’d be better off doing Bonjour syncing than using OneDrive.
You couldn’t sync to DEVONthink To Go via OneDrive in any situation.