Chase family of cards also an interesting play for Delta if you already are covered for lounge access and helps you diversify.

Transfer to both VS and AF for DL flights at reduced rates (especially VS) plus let's you tap into UA and Hyatt for other plays.

Personally I have AMEX Plat for DL lounge and 5x airfare (and use up the Uber and $200 credit so it needs even) plus the AMEX EveryDay for 2x groceries plus 20% bonus with direct transfers to Delta.

And cover Chase with the CSR for non-flight travel and dining plus CFU/Freedom for everything else (especially Costco due to Visa requirement).