I'll second this observation, though I won't say "always" running at high CPU on macOS.
I will find periods when the "Evernote Helper (Renderer)" is running at high CPU. See attached. It will run like this periodically for several minutes, then reduce it's usage. All-in, though, it's been high for > 50% of the time I've watched today.
I haven't yet been able to equate those moments to when something might be happening in Evernote. It's NOT when a sync is happening (as far as I can see).
Also, this thread should be in a main Evernote channel - not "Integrations". I may cross-post there.
Environment:
Evernote 10.5.7 build 2171 public, Editor: v114.1.14753, Service v1.25.2
macOS Catalina 10.15.7