Reduce CPU usage on disabled tracks
I notice that when I disable a track that this will not reduce CPU usage. In contrast disabling individual modules will reduce CPU.
This is probably because the two mute styles "Audio" and "MIDI" that are not designed to completely stop the processing.
Distinguish between muting and disabling. Muting a track will keep the engines running, but disabling will stop all modules. For the UI I would suggest to keep everything as it is, but put a "real" enable / disable behind the "Enabled" switch that can be found in a tracks properties.