Accountsd using lots of CPU constantly
You could try using the Console application to see if accountsd has recorded any errors. Just open Console and enter "accountsd" in the search filter in the top-right corner of the window.

accountsd doesn't just deal with iCloud accounts. It appears to handle all of the accounts listed in the "Internet Accounts" pane of System Preferences. You could try disabling them all, then enabling them one by one to see which one is causing the issue.