Climate zone 4. I have a small addition and I need to insulate a portion of the floor in this addition. I consider this construction a sort of breezeway since on one side of the addition  is supported by the house foundation and on the other side is a separate foundation wall just to carry the framing for this addition, so it is open at both ends allowing one to walk directly under it. So it is this portion of exposed floor that I need to insulate. The framing bays are about 8 inches in depth and I have access to the framing bays from the exterior side. I was considering gluing foam board to the floor sheathing and seal around the perimeter any gaps with can foam, then have the insulation Contractor spray open cell spray foam over the foam board to give enough thickness to meet code compliance which I believe is R19.  I really want to make sure this floor assembly is well air sealed so I’m wondering if I should eliminate the foam board and use a few inches of closed cell foam. Or should I fill the framing cavity with open cell only? Should the R value in this case be higher then R 19 due to the exposure, which would primarily be wind blowing across the  exposed underside.  I was thinking I should install  a foam board over the  face of the bottom of the joists to help with thermal bridging. Does the face of the insulation in the framing cavity have to be in contact with the  back of the finished material I use to close up the exterior side of the floor?
Thank you   PS there are no mechanicals in this floor assembly.