Z settings for photographing upper antelope canyon during canyon….

My gear consists of a Nikon z5ii, 20mm 1.8f S and a SB-500. I typical shoot in aperture priority, auto iso and AF single. When I need to use a flash, I go full manual, with a helping of trial and error to dial in exposure (I’m not the fastest, and I hate shooting under pressure)

Does anyone have any tips or tricks for photographing upper antelope canyon during a sunny, mid day guided romp? I don’t have any idea of what to expect with iso, exposure, color temperature, flash usage, best place to be in the group, how much time we have, etc.

I’d like to come out of there with some keepers so I’m looking for any help. Thanks in advance.