I recommend caulking the stud/OSB joints, and at the plates also, to stop air infiltration/exfiltration, pp.21; http://www.engr.psu.edu/phrc/trainin...ngbarriers.pdf
Especially with air permeable insulation; fiberglass, rock wool, etc. Though, north of me they vent the cavities, you wouldn't need to patch the holes- lol. Read the ink stamp on the sheet interior face- "sized for spacing"; horizontal application in Canada for these grades, Table 2:http://osbguide.tecotested.com/pdfs/en/tb104.pdf
Notice spacing gap after Table 3.
In the U.S.- either upright or horizontal with shear blocking (if required).
Be sure there is a gap or you will have problems; http://www.ewpa.com/Archive/2006/aug/Paper_266.pdf
And be glad your OSB is applied vertically; "Yet, there is one simple aspect of this technology that many people do not understand, namely the placement of OSB boards horizontally or vertically. Some “scientists” advise holes and gaps between OSB boards to accelerate “drying” not realizing that actually they promote wetting of the wall. Thus the construction practice goes towards another trap. Horizontal placement of OSB improves (marginally) racking strength allowing the usage of 3/8 inch thick board instead of ˝ inch while destroying airtightness and effectively all aspects of hygrothermal performance.
Yet, the solution is simple, use only vertical placement of the OSB boards. Vertical placement provides most joints on wood studs and ensures long-term OSB performance and effectively durability of the wall." From; http://best2.thebestconference.org/pdfs/033_EE9-4.pdf
IMO, the gaps between studs is not near as important that the wall is out of plumb the width of the gap between plates just above the studs. Get a few of those and your drywaller will scream...
See if they stuff fiberglass in the window gaps to framing, you will know he doesn't care/doesn't know; read just below #8
Insulate your rims with foamboard/canned foam or pay extra to have it done; 2nd floor rims also; http://www.buildingscience.com/docum...l_seal_rev.pdf