I would use expanding foam in between the studs and wall, then 1-1/2" to 2" of pink insulation inbetween the studs sealing the gaps with expanding foam again.
The pink foam at that thickness gives you the required vapour barrier anything thinner will not work as a vapour barrier.
Do not use fiberglass with the paper backing that will create a double vapour barrier, which you do not want.
Other methods would be to spray foam everything, costly but eliminates your problems of gaps behind the studs, vapour barrier needs, etc.
The pink foam at that thickness gives you the required vapour barrier anything thinner will not work as a vapour barrier.
Do not use fiberglass with the paper backing that will create a double vapour barrier, which you do not want.
Other methods would be to spray foam everything, costly but eliminates your problems of gaps behind the studs, vapour barrier needs, etc.










































