Good question Zean. First the hub motors on the hybrid and the Mountain bike are 500 watt 36 volt. The fat tire bike is 1000 watt 48 volt. 746 watts equals one H.P. none of the motors have gear reduction just straight direct drive so the torque effect isn't super high either.
Here's where my answer gets a bit iffy. All three of my forks are regular bicycle two are steel and the M.B. is a decent after market Rock Shox aluminum. I prefer the steel, not as prone to cracking, but suspension forks in steel aren't very common. I like the ride of my full suspension mountain bike so there's that. The fat bike I'd planned on getting a suspension for but the big tires ride nice and I'm going to stick with what came on the frame. It's an inexpensive Mongoose but the fork seems ok. The classic spring girder fork on my hybrid is strong enough for a light street motorcycle so no worries there. Some regular bikes from Wally world, might be a problem with even 1000 watt direct drive, unless you add a torque arm from the motor to the fork. I personally wouldn't run a front e-hub on a cheap aluminum fork...period, even with a torque arm. I may be overly cautious on this.
I'd think those that have decent quality aluminum frames and forks would be better served running a rear e-hub, especially if you go off road or really knarley back roading
. The bikes just hook up better with rear wheel setup. I like my front wheel setup on the street but give the front wheel drive a five on ten scale when the gravel or sand gets deep. Locking the front suspension on the M.B. helps, but still just a 5 with motor assist.
Now brakes. The hubs come rotor disc ready and adapters are readily available for the calipers. If you go disc I'd suggest 203mm & caliper adapter to match this offset. These hubs are big and some calipers aren't going to the clear motor housing with smaller rotors.
Rick C.