Inner corner with corner profile and double gypsum

[Jasse64]

I have been renovating a house for many years and now I am at a point where I am unable to find answers. We are planning to soundproof one room in particular and have chosen to use double gypsum board outside the plywood. To reduce the risk of cracking in the inner corners, I will use metal corner profiles. The question is, should the profile be fixed to the plywood sheet or inside?

 

[Tjrex]

Between plywood and plaster.

 

[Jasse64]

Between plywood and gypsum.

Thanks, I suspected it but sometimes you need a bit of help along the way.