Area was existing when I bought it. I added some supplies and a return for the HVAC.
Ok in the winter... too hot in summer. I found the rafters on the one side had no insulation(above the drywall) and the other had. The short section in the middle also had none.
The rafters go down to the perforated soffit. Have gable ends.
I've read that I need to allow an 1" space between insulation and the roof sheating for air flow. But my contractor friend says to have insulation blown in there and completely fill rafter areas and increase the size of the one gable end(too small). He says not completely filling area...leaving the gap...I would create moisture. Basically explained as the warm the the roof would meet with the cooled or cooler insulation below..it would get wet??

Side note: I replaced the wooden sealed soffit last year with aluminum. I punched an 1" hole in the wooden soffit about every foot throughout.

Did you insulate the ceiling of this space, that is where you will need it most? Tapping into an existing hvac system will not always give you the results you want, the system may be overloaded or the fan too small to circulate this much air. It is common for 2 or 3 story homes to need some opening./closing of supply and returns when you switch from heating to cooling.

I'm confused.

You titled your post "insulate a converted attic living space" .you don't speak of how you are converting it. Are you insulating the ceiling joist or the roof rafters? If insulating the ceiling joist you would leave a opening between the insulation and the roof sheathing for air circulation. To not do so would create condensation when the hot air trapped in the attic is cooled (such as at night).
You said that you contractor recommends bowing in insulation in the rafters. If insulating the rafters you would not want air space. The warm air cooled by the air conditioning in the summer would cause condensation. However if you want to put in an air space, it would be next to the roof sheathing. There are Styrofoam baffles for this.

Personally I think I would want a moisture barrier next to the ceiling drywall, just like any other wall, to prevent condensation in the winter when the warm air inside meets the colder outside.