The standard contract almost certainly signed over all rights to TSR. There may have been some folks who got better deals, particularly regarding fiction/comics.in yon olden days if you got published in Dungeon or Dragon magazine was the understanding that you owned the content you produced or WotC did? Not talking reality here, I think that turned out complicated for WotC.
Also you could use WotC IP.
The thing that bit Wizards regarding the Dragon Magazine archive was, I believe, two-fold:
- The oldest contracts had been scanned for archival purpose. And were stored on an 8-inch disc. Which they no longer had the ability to read. This is why the Dragon Magazine is basically a photocopy of the actual magazines instead of turning them into more useful formats – they figured that making the archive a facsimile of the originals would be safe.
- Apparently David Kenzer and/or Jolly Blackburn of Kenzer & Co/Knights of the Dinner Table did have some special deal in their contract, and threatened to sue. They negotiated a deal that let them call Kingdoms of Kalamar an official D&D world, as well as publish Hackmaster as a parody version of AD&D.