It appears each contractor is "designing" his own system.
I suggest you look at two web sites and set your own standards.
NRCA (National Roofing Contractors Association) has lots of
construction info.
Building Science Corporation has researched climate specific systems
information.

How does the first contractor know he has to take off all the roof
sheathing?
Have you been in the attic to check for leaks and deterioration that
would suggest that is needed?
IMHO, a low sloped roof in the Poconos needs ice & water shield.
If the under roof area is to be vented, it is my belief that soffit
vents with ridge vent is the way to go.

TB