When I was cycling with my old Roadie club some days we would average 24mph over a fair distance. Bearing in mind your taking your turn on the front in a rotation system and your less than a wheel apart this was easy to do (with concentration), and some days faster.
Even on my mountain bike on a...
Not a fan of fat bikes, unless i was near a beach or in a cold / snowy environment etc. I've ridden one on the road and the tyres were very noisy. As said, great for certain conditions, but not ideal for majority road riding.
Welcome to the forum. I'm relatively new on here compared with most. I'm sure you'll get some great advice ref bafang motors. Good to see how this forum is growing.