I'm in agreement that you're not going to feel/care a whole lot about mix-and-matching your wheel sizes to your bike frames. In fact, I consider that ability to be a plus to disc brakes. Just be careful cornering, especially with large pedals.

Also, I like my tongsheng motor too- I never rode a bafang but the tongsheng gave me exactly what I thought I was going to get. I also MIGHT have gotten the built in brake light levers they offer, but like you, I use hydraulics (and it keeps the electric system and the wiring a bit simpler). Are you using some kind of device/switch that attaches to the levers?