Roof: composition shingles on solid decking 4:12-12:12 pitch
Attic: soffits vented to ridge vent
HVAC: gas heat in attic
Garage: 36" 1/2hp whole house fan in ceiling, auto dampers

Foam Insulation:

.... Pros & Cons?
1) Only on attic floor
2) On rafters, sealing off vents & fan + venting HVAC

Check your shingle manufacturer's stance on how they handle warranty claims when spray foam insulation is involved. Worked for one of the main manufacturers as a sales rep for a few years. They were fairly anti-spray foam and would point to that as the cause of shingle issues due to the attic not being able to breathe.