I put a Swytch conversion kit on one of my drop-bar road bikes. 250w front wheel drive.
Thumb throttle on a bar extension that hangs below the left bar flat. No pedal/crank sensor.
It turned my 20lb bike into a bit of a behemoth at 30lbs, but I reckon using the electric assist only 20% of the time.
Not instantaneous power. Nor does it sustain wheel power for more than a few minutes. Limited to 20mph on level terrain.
Great for helping on a short uphill or getting thru an intersection quickly. Not bad for $600 total.
Contrast it to a nice Specialized Creo priced at $5k, mid-drive powered but no throttle. Would love to own that Creo.