I've just downloaded Photos 1.7 and I've checked the performance settings and Hardware Acceleration isn't available for my GPU, but I think that it should be. I'm running an old cheese grater style Mac Pro, but with High Sierra and an NVIDIA GTX 680, which is an Apple Metal supported card. My graphics card isn't listed under Hardware Acceleration and instead it states 'no compatible GPU'. I've checked my Graphics information on the System Report and it states 'Metal - Supported, feature set macOS GPUFamily1 v3', so I would expect it to be compatible. Does Photo 1.7 have additional hardware requirements for Metal support?