I may have stumbled across a solution to the high CPU usage, at least for me (Windows 11 user, as per my previous post), posting here in case it helps others who don't have a workaround.
I disabled "check spelling while typing", quit and restarted Evernote, and noticed I was back to an appropriate CPU usage (<1%).
Re-enabled the setting (it's handy 🙂), been about 45 mins and CPU usage is still perfect and stable when I'm using the app or not.
YMMV!