CUBASE 12 CPU is at max load with only a few tracks

[Chriss]

This might solve your issue:

Cubase 12 Upgrade ASIO-Guard Issue

I had the problem of CPU overload causing major audio glitching when running a single audio track and one VST effect (Helix Native or Amplitube 5) on Win 10 PC, i9 processor. Solution turned out to be simple. Just had to activate the Steinberg Power Scheme in Studio Options. This is set to off by default in the update and the setting does not get picked up from the preferences. Certainly worth checking if you have this problem.