Hi,
Can two workspaces have a same preference center?
Yes, but why don’t you explain the business requirement you’re trying to meet here?
In theory, yes. The items listed below are sharable across separate Workspaces. Provided your preference center doesn't require any items that aren't among this list, there is no reason other Workspaces could not access it.
Email Templates
Landing page templates
Models
Smart campaigns
Smart Lists
Snippets
Segmentations