I'm just curious the metal feature set of two iMac models on 10.14(Mojave)
iMac (27-inch, Late 2014) iMac15,1
iMac (21.5-inch, Late 2015) iMac16,1 or iMac16,2
The table in this page MTLFeatureSet shows:
"iMac models from 2015 or later" will be macOS GPU family 2.
I hope that people with these models will help check,or who can give a answer directly.
Two method for check:
1.Press and hold the Option key while choosing Apple () menu > System Information. In the sidebar, select Graphics/Displays.
2.Or terminal command
Metal: Supported, feature set macOS GPUFamily1 v4