I ended up emailing, and then received a phone call from Disney regarding this exact issue.
Luigis flying tires- you can be wheeled right up to the attraction and then transfer in two steps. It is an 'up' transfer from the actual tire to the seat...and then vice versa to get back out. Sounded like it is pretty easy transfer.
Maters tow- just like transfer at thunder mountain railroad or some of the attractions in fantasyland. Cart has a moveable hinge door that allows for more space to transfer in. Slight drop or completely parallel from what I understand.
The racers ( forgot the name at the moment) - like a space mountain transfer. Additional car available for extra loading time...and it has a higher seat so it is more of a parallel transfer and then down to the seat, rather then all the way down like in pirates.
All lines are ADA and then split off at the end for extra assistance.
Hope this makes sense and let me know if anything is confusing.