We have gone on many tours with my son who uses a manual chair. There have been several where people stayed in their
ECV or used a disney manual chair. The tours we have taken:
Wild by Design - two times
Back Stage Safari - two times
Wild Africa Trek - one time
Mickey's Magical Milestones
Marceline to Magic Kingdom
Flower and Garden Festival - Epcot Garden Tour
Behind the Seeds
Undiscovered Future World - this is long, for us about 5 hours, and a lot of walking if one is thinking of trying to walk it

I think there might be more, but can't remember. We enjoyed them all. No problem with the wheelchair.
Also, we have done the kinds of things where you learn a lot of info that aren't exactly tours:
Lunch with an Imagineer at Brown Derby
Untamed Lunch with an Animal Trainer at the Sanaa (this was so good we did it twice) We learned a whole lot and we all got to sit down and eat!
Also, we have done the little free tours at the hotels and at the world showcase (not sure how many of these still exist)
Hope this helps.
Have fun