SOme of your questions may be determined by your party - kids? The dining plan can be an even better value for kids than adults, LOL. The cost of one day on the DDP is often less than the cost of one character meal… and the kid will get an additional CS meal and “snack” as a “bonus”!
We are going to try the DDP on this upcoming AUgust trip for our fam of five (we have 2 kids aged 9 and 5, but also an 11 yr old Disney sadly mistakes for an adult :sad: ). That said, we have always done the grocery run before, so it will be a new experience for us! For our groceries, we tended to drive out to a Publix or Super Target or Walmart. I usually can’t bring myself to pay the prices at Goodings or the resort stores. I have used them in a pinch but that’s about it. Have not used a delivery sevice - but if DDP hadn’t come along, I would have! Had it on my to-do list for this coming trip… and then DDP came along!
B’fast foods are ALWAYS good to have on hand. Even with the DDP, you will probably need b’fast food a few days to cover what DDP doesn’t. Our family is usually too excited to fully enjoy a big sit-down b’fast anyway - we’re all itching to get in the parks and go, go, go! We do better with sit-down meals at lunch and dinner. Normally, we would plan on b’fast in the villa, and pack some snacks to nibble while in the park. (Tortilla wraps pack very nicely in a small soft-sided coooler with a bottle or two of frozen water! The water keeps em cold, then is drinkable later as needed). We enjoy sit- down dinners at the parks - gives us a rest, and usually the food is quite good. The ddp does have you dining at CS half the time, but not all counter service is burger/fries fare. There are some nice places with everything from soup to stuffed potatoes to noodles to turkey legs to salads to you name it. We have cooked dinner in our villa too - it’s nice sometimes to just relax at “home” and have a meal in. Some foods work well for later days (i,e, cook a big ham or roast for dinner, then use it for sandwiches the next day.)
I second soxmets in that snacks are good to have on hand! We usually have micro-pop popcorn packets and ice cream on hand in case either sweet or salty is the snack of choice, LOL.