I originally posted this in the tonneau/multipro-tailgate thread, but seems like it'd be useful to put in this thread to have it all together...
https://extang.com/trifecta-2-0-signature-series
I have an AT4 crew cab with the MultiPro tailgate, and I have an Extang 2.0 Signature tonneau, a soft tri-fold type. My previous Sierra, I'd just throw a tarp over everything, decided I'd at least try out a tonneau with my new Sierra. Overall, I've liked it. Installation was included, so I didn't install it myself, but I watched and talked about it w/ him as he installed it, explaining various things about them to me. It's a tri-fold, but it doesn't lift up against the cab's back window, it stacks into the 3rd segment's position against the cab: if you need the whole bed exposed, you'd have to remove it. Has been a 'little' hassle once, but, it was easier to deal with not having the entire bed open than it was to bother to remove it.
So, here's the thing about it, in conjunction w/ the multipro tailgate: the whole tailgate opens fine with the tonneau in place. The tailgate will close fine, if you’re closing the ‘whole’ tailgate. If you drop the inner tailgate, that's fine too. The crux of the problem is, closing the inner tailgate with the tonneau latched closed: the entire tailgate will close with the tonneau in place but the inner tailgate's arc is a little higher, and collides with the tonneau. You have to reach in and unlatch the tonneau so you can flip it open so you can first close the inner tailgate, *then* open the entire tailgate, latch the tonneau back into place, then close the entire tailgate. You would think, if you have the tonneau in place and the inner tailgate open and the main tailgate closed, that, if you couldn’t just close the inner tailgate (as you would think you should be able to), then it should be easier to open the entire tailgate, close the inner, then close the entire tailgate: however, if you have the main tailgate closed with the inner tailgate open, it doesn’t let you then open the entire tailgate until the inner is closed. A bit of a nuisance, but, I can put up with it.