OS Contacts has been very buggy and slow

My Contacts app on MacOS (presently at 14.1. on 2018 Mini) is very buggy and slow/beach ball of death. This has been going on for quite a while even before the OS updates. I have seemingly created/imported multiple Contacts which in some instances will show up as 4 to 6 identical entries.

I am surmising, fearfully, that the only way to remedy this is to designate my iCloud Contacts list the master copy by going through ALL my contacts and ensuring that I remove duplicates from non-iCloud databases and then see which ones fall outside the iCloud master and manually enter those stragglers into iCloud. Is that the most foolproof method? Asking before I plunge headfirst into that rabbit hole.