The ePO services themselves should be running as System, so the only thing that would really be affected would be SQL access (assuming that ePO is using this account to access the DB.)
Check the settings in the config-auth page, and adjust accordingly. Make sure you use the "test connection" button
Thanks for the advice! After renaming the local admin account, we change also the config page and rename the login account in the SQ DB. And now its working fine!