REGEN is always 'On'... but regen with one-pedal driving is a different story, with 'more' feel of the regen slowing you, and even bringing you to a COMPLETE stop, and even HOLDING you at the stop.
REGEN without one-pedal on is simply not going to feel quite the same, is going to allow for more 'coasting', and will require more of your own input with the foot brake, although the weight of the truck is going to put a lot more pressure on the brakes than in any other EV before.
I would hope that there is a 'REGEN LIMIT' setting, of sorts, to allow the driver to manage or 'set' the amount of REGEN they are comfortable with. One recent new owner stated that he didn't 'like' the one-pedal driving action since when he came off the 'go pedal' he expected to coast more, but the one-pedal provided 'too much' REGEN for his liking. I would like to see that customizable setting, myself. I've owned and driven Nissan LEAFS for some time, and love the ability to allow it to do it's 'normal' REGEN action, or to add it that by putting the gear into 'B' mode, which provides MUCH MORE Regen, depending on the situation. In traffic, I certainly LOVE the 'B' mode, but if coasting is more desireable, such as down hills, then I don't want it.