My vB3.8 forum has close to 200 forums with 48,854 posts and 5,189 Members and is closed.
My Drupal forum has say 40,000 registered users. Not very many posts.
We are using a separate membership database for usernames and passwords so we can have a single sign on. That is why we have so many registered users. That part seems to be working.
Many of the usernames are the same in both forums.
Both forums have a similar forum hierarchy. But not exact.
So here are my plans.
A. Use impex to import Drupal into my vB3.8 forum then import to XF.
B. Use impex to import Drupal into a clean install of vB3.8.
Then merge the two vB forums before importing to XenForo as a whole.
C. Import Drupal to vB3. Import to XenForo.
Import 2nd vB3 forum into XenForo.