ProTools and Mojave to Monterey . . .

[kj]

Are you using an interface, or the built in sound? Sounds more like the driver is taking a dump, as that should be plenty powerful to do what you are doing (doesn't sound too intense). But being able to run low latency has more to do with the drivers than your hardware. Have you tried other programs? I bet even garageband would be less problematic, and pretty capable.