We went by Eurostar and stayed in the DL Hotel, so can't answer your other questions, but we did the character breakfast at Plaza Gardens and it was great, we got loads of photos and DD loved it.
We didn't get any meal plans, as we wanted freedom to eat when and where we wanted, and not spend loads of time sat down eating and that worked for us. A meal plan would have cost us a lot more than we spent on food.
We ate at the Lucky Nugget twice, Caseys Corner, had one character breakfast and one Princess dining, one room service, and had crepes by the balloon one night.
For breakfast each day, we bought 2 x 8e breakfast which was coffee, juice and pastries, to share between 3 of us, and bought 1 extra pastry. It was the cheapest way of doing it when we went in 2019.
We also took snack packs with us from home for mid day, and usually found somewhere to sit and eat them, and just bought coffee and cold drinks and ice cream when we wanted them.
We went for the "trip of a lifetime" and have been saving like mad ever since to go back and do it all over again 