Diffusion-open vapor barrier or PE foil with rear ventilation

Hello everyone,

we are now at the roof insulation stage and have planned the following structure from the outside:

on the slopes:
tiles
underlay membrane (vapor permeable)
20cm glass wool insulation (directly on the underlay membrane on the slopes without ventilation)
vapor permeable vapor barrier
battens
drywall ceiling

in the attic:
tiles
underlay membrane (vapor permeable)
cold attic
tongue and groove boards
20cm glass wool insulation (directly on the boards without ventilation)
vapor permeable vapor barrier
battens
drywall ceiling

First question:
if the vapor permeable vapor barrier releases moisture back into the interior in summer, wouldn’t the moisture then accumulate in the drywall ceiling?
Should the drywall ceiling be ventilated somehow, especially in the bathroom?

Second question:
my roofer recommends a different structure. Instead of the vapor permeable vapor barrier, a normal PE foil and ventilation everywhere of 4 cm installed. That means enlarging the rafters (currently 20cm).
Which solution do you consider better?

Best regards and many thanks for the answers