I agree with this, but I don't need to be a guinea pig. Among currently 'proven' cold climate choices I would choose LEED 10 before the remote wall system recently advocated by the CCHRC (cold climate housing research center) at UA Fairbanks. The trouble with the REMOTE system is those darn 9" screws sag over time, leaving a gap in the insulation envelope at the top of the walls where they meet the ceiling insulation.
When/ if I do build I will be going with the latest greatest proven tech, distinct from the latest/greatest tech that should work.
And I am putting in AC. If I build, it is simply not negotiable. Summers up here are now too dang hot to do without a couple mini splits pumping cold air while the sun is shining anyway. So the insulation envelope will need vapor barrier inside and out; and there will be solar panels.
I agree that building a high performance (R and air sealing) envelope is a rather technical business, and depends on the local climate as well (not just snow loads). You will want to find a builder with a track record, and not go for any solutions that are too new.
Its been awhile since I really studied this stuff, but I would think that you would go for a double-framed wall, 2x4 inside and outside, with minimal thermal bridges between. Wall might be 12" thick. Studs can be staggered (hard) or aligned (easier to build, bridge effect is small due to gaps). Window and door openings and sills, and top plates use plywood to span between the two frames with low thermal bridging, and the whole cavity is dense-packed. Airsealing is by conventional (permeable) wrap on the outside... no foam anywhere. A simple HRV is installed for fresh air.
Despite your latitude and snow loads... I assume you are close to the coast, and not as cold as the mountain provinces.
AC will be trivial, probably less than 1 ton. I bet with good insulation a dehumidifier would almost cover your needs, but a single minisplit will do the job.
'Vapor barriers' (like poly or visqueen) are frowned upon in the lower 48, often causing more problems than they supposedly solve. You do need a air barrier (which is vapor permeable to allow drying as needed), but a single one on the outside is almost certainly all you need. The problem with foam is that IT is a vapor barrier, and if too thin then you get condensation in the cavity, much better to skip the foam entirely, also getting rid of the long screws. The mass of cellulose would provide a large amount of water vapor buffering, and would reduce the need for indoor humidification/dehumidification in both warm and cold seasons.