Hello,
You can delete the tags themselves, but you can check the V12 equivalent of the tag you’ve mentioned
tag:#AK_Step1_v12::!FLAG_THESE_CARDS
I personally don’t touch them, we have gone through and deleted a ton of duplicates off of AnkiHub.
You can delete all cards that are not apart of v12 anymore by following this tutorial: How do I delete all V11 cards after I have upgraded to V12?
To delete V11 tags: Why do I still have V11 tags in V12?