Something that wasn't obvious to me and which has a huge impact on your developer experience in Xcode 27:
The Device Hub sometimes doesn't kill CoreSimulator processes when you quit the app (not sure if this is a bug or intentional). Given that each device uses several hundred processes, the memory/processing impact is significant.
You'll probably want to keep an eye on how many you have running: use right-click on the simulator in the list to "Shut Down" as necessary.