Depending on the year sub 2024(I think) it's been well documents how low it was due to the lack of CPU power and there are hacks out there to trim the apps to gain cpu/ram back to. 2024+ got an upgraded CPU and ram so it's supposed to be better/
They still have CarPlay and don't plan on stopping it. I just got back from a car show and asked around — only GM was a firm no. However, they confirmed their software will be Android-based and should support the same apps available in the Play Store, though it’ll obviously be a subset like it is now. Apple Music will be supported, but not Apple Maps and probably not Apple Home, which has more to do with Apple than GM.