A bit stretchable is of course of advantage for the curves.
A/B/C pillars are usually w/o padded back.
If you remove all old foam material etc. from the headliner and have it very smmoth, then you also do not need the foam. The foam is as I believe for a bit sound absorbing and it is a great help to cover uneven headliner board surfaces.
Some people buy the foam as separate item, glue the foam first on the board, then the fabrics onto the foam.
The glue must withstand temperatures up to 100 degrees Celsius later. That is the most important point.