... and I forgot to add: with the recommended 800asa colour negative, what speed am I best to rate it at to help ensure opening up some of the shadows especially since there may be significant light variation in the wider angle images, and if the film is a bit contrasty? Am I best just to rate it at the nominal 800 or say 640asa?

I was told that Portra 800 is not very contrasty, so maybe I'd simply expose for 800asa; whereas I was told NPZ 800 is a bit more contrasty.

Also, with the B&W 1600 negative film, should I expose for a somewhat lower speed for a similar purpose if the film tends to be contrasty (as I do with XP2 when shooting it - 250asa instead of 400asa)?

Many thanks again.