Why Notes app use a lot of resource/energy?
Solution 1:
In an Apple communities thread I found this:
Jan 11, 2021 12:58 PM in response to madmac88
After chatting with Apple support - the problem seems to be related to one (or both) of the 2 non-iCloud accounts that I have set up for Notes. After disabling Notes sync, Notes is now no longer hogging energy!!
It seems to have worked so far, I did have an additional 2 accounts with notes being synced. I have unchecked the sync and at the moment the notes app does not seem to being consuming the energy it was. I will continue to test and will update again.