I was hoping that someone more knowledgeable would answer this. I think they best community to look at is Endless Sphere[1] but you could also check out /r/ebikes[2] (although I warn you you that they are all about making DIY bikes that are unnecessarily powerful in my opinion.

Then there's electric bike review[3]. He's reviewed an incredible number of different bikes.

[1]https://endless-sphere.com/forums/ [2]https://www.reddit.com/r/ebikes/ [3]https://electricbikereview.com/