I use macOS Big Sur on my MacBook Pro early 2015.
Usually, I very rarely open the Notes app, I just using it for copy-paste only, maybe 4-10 times or 2-5 minutes in every 12 hours, but usually I leave the app running in the background. When running, even though I haven't opened the application for a long time, CPU and Energy usage is very high compared to other applications that I almost always open and actively use such as Browsers and IDEs.
here is my activity monitor that show energy impact of the Notes app:
here is CPU usage:
I don't know when this behavior started, but as I remember it was a long time ago. I always hoped it would be fixed in an OS update, but this happening continues to this day even though there have been several updates. Is this happening only on my MacBook or is someone experiencing the same thing?