On the fork, "triple clamp" / triple-whatever
is definitely stronger. I just went with that on SB Cruiser a few weeks ago, and it's much much stiffer (less flexy) than anything I've used before. I built mine from clamps Chalo sent, and some old bike frame tubes and some steel lowers off a cheap suspension fork (until I can build the dropout modules I want, that have specific stuff that doesn't come on anything existing).
What I built so far
Mockup of something like what I will end up with
Mine are nonsuspension, but they work just fine on SB Cruiser, riding on typical roads at 20MPH; even the average potholes are ok with them, though it's naturally bumpier than with suspension, it's not that much different than any of the cheap suspension forks I've ever had. I didn't expect to be able to deal with the ride, but it's really not enough different from before to worry about on most of the roads I ride on (there's a few places I wish for suspension). I may add suspension at some point, or I may not. The *rear* of the trike needs the suspension a lot more than the front, given the loads of a St Bernard or two, or a bunch of big dog food bags, or a full mounded-over cart of groceries....).
If you want strong, off the shelf, but no suspension, then you can use pedicab forks. That's essentially what I have, though I used my own tubing/dropouts. Places like this https://precisionpedicab.com/ sell most of the stuff you'd need to build and/or motorize a pedicab, so you could probably use the same stuff for yours. You'd have to poke around to find the places that have all the bits you want (or ask Chalo; he could probably tell you).
I'm using the Avid BB7 disc brakes, cable operated, AVid speed dial lever, 200mm rotor, whatever pads came with it, and they work fine--more than enough power to skid the front wheel. Rear brakes are just regen on the DD hubmotors; adequate but not presently adjustable--is just full braking or none.
I do recommend a long trike for 20MPH; SB Cruiser handles pretty well, though I have stuff I'd change if I were to build a Mk II. IIRC it's around 11 feet long ATM, not including the trailer hitch.
It's not all that wide; yours will be wider as a sociable, which will make it more stable in turns if the seats and other mass is low enough. I am not sure if it is the width-to-length that makes SB Cruiser stable, or just the length.
