@rollasoc and SoundOf: your issues sound more like a performance issue than the problem with VST3 abnormal CPU usage.
Easy test: load a problematic project and disable the “Suspend VST3 Plugin Processing when no audio signal is received” preference in Cubase - if the CPU load is not immediately and heavily reduced (between 50% and 100% reduction), then it’s something different.
I’d recommend to check out the trouble-shooting guide, check if the project’s layout has a role (check different plugins distribution, check that there is no heavy multi-timbral VSTi routed to a heavily processed group, etc.) and please open a separate thread in case the issue persists.