Right now I keep getting pulled back to bionx it is just sooo much $$$$.

I'm really looking for an assist and from my previous experience with controllers (mostly non ebike) most just limit the voltage which really just limits the RPMS in these motors (speed) and it'll suck as much amps as it controller can dish out. Is this the case for modern eBike controllers?
That is really why I am drawn to the bionx because it can do partial assist based on my output so it is a booster type assist.
I'm really looking for a current or wattage limiting controller. Assist me 50, 100 watts or 200 watts with a flip of a switch?

Maybe I'm just thinking too much about this. Just wish there was a place I could go to test one out before I buy something that is so much $.