As far as how much PAS is needed, I would imaging that the weight of the bike is not extremely relevant, unless the motor is undersized. The biggest factor is probably rider weight which tends to have a wider range of variance.
For me, bike weight is most relevant to handling/transporting/servicing it.
Most ebikes have various levels of PAS, so when you combine rider weight/cargo weight/intrinsic bike weight together (along with other factors which affect the work the motor has to do, such as tire size, incline, wind, surface, etc), you should be able to dial up a PAS level which gives you level of comfort you’re looking to achieve.