I can't comment on a 2.0T with AFM but I can on the Acadia V6 with AFM. Did not notice any performance issues when it dropped down to 4. With the Denali I could not see when it dropped on the DIC like you could on the lower trim levels, but you could see the instant mpgs jump up in the 40s - 50s and sometimes 99.
Not sure what AFM would do to a 4 cylinder.
2018 FWD Terrain Denali, Steel Blue Metallic, 2.0L Turbo, Sunroof.
2017 FWD Acadia Denali, Crimson Red Tri-Coat, V6
2014 FWD Buick Enclave Leather
2012 FWD Equinox 2LT V-6,