Hello, I tried importing mr pankow deck as a separate deck alongside already having ANKING MCAT deck, and it said 1700 imported, 789 could not be imported , Went on reddit and said its because of duplicates , im assuming since both PSY SOC in anking and Pankow. Can i delete the duplicate cards from the ANKING MCAT deck or is it useless since everytime i load up anki, the cards will show up due to synching with Ankiweb if that makes sense?
Hello,
I would be happy to help. 
It’s a little hard to predict what will happen with multiple decks in place from shared lineages. In most cases, since Pankow incorporated his deck into the AnKing deck, though, the recommendation would be to just use the AnKing deck
You can try deleting cards if you like, and they may not be repopulated, though I’m not sure if that can be entirely guaranteed. It may be that they are re-synced, or that they end up overwriting other cards, or creating duplicates. It depends on a few factors that can vary, especially with other decks shared online.
Please let me know if that answers your question, and if there’s anything else I can help with.