So confused on how to insulate Michigan Bungalow

I am getting so many mixed signals on how to insulate the upstairs of my bugalow. I have narrowed it down to two.
The upstairs is completely refinished wonderfully with a great wet plaster job. The knee walls on each side have virtually no insulation. The side of the kneewall going up the inner wall has some thin fiberglass batts. I have 6 roof vents across the top of the roof and a gable vent at each end.
This room is as cold as ice in the winter and hotter than you know where in the summer.
Contractor one would like to add a couple of vents on each side in the knee wall area and blow in cellulose to the knee flat to an R49.
Contractor two, tells me everyone will want to add vents and he wants to use Icynene foam insulation across the top the of roof, therefore "encapsulating" the room and make it livable. He says there is no need for ventilation since we are "blanketing" the entire upstairs from the roof down.
I am so confused and need to do something soon to make it livable this summer.
Please advise.
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