I attended the WC game, parked in Lot 1 near the Fieldhouse. People were able to sit in their vehicles and "prepare" for the game, some others sat on tailgates or stood outside their vehicles without much of a problem. Fans were definitely far more discreet than they otherwise would be at a tailgate party in non-pandemic times. You should be OK with already prepared foods. There were security patrols in the lots on golf carts. I would advise against trying to use a portable grill.
Entry/Exit was breeze. We were able to walk in ahead of the designated entry time through the assigned entry gate and after the 90 minutes before kickoff cutoff time that was indicated for general entry. There's some flexibility with it but I would recommend going in within 15 mins or so of your assigned time. The assigned gate will be noted on your ticket, and is based on the lots your parking pass (emailed before the game) will assign you to as well.
Have fun and be loud for us all!!