99% of other products will work fine on the explorer rack unless they have a proprietary rack they are designed to work with. I use Novara panniers on mine all the time and they fit perfect.
The issue isn't other products working on the the rack its the Topeak bags not working on other racks because of the proprietary slide track mounting system.

Most trunk bags have a strap at all four corners that wrap the outside rail. They as well as panniers that hang on the rail will work fine on the explorer.