Specifically, can you hollow out the veggies or even stuff them and store in fridge the day before you bake them? Or would this compromise the dish?

I do a lot of stuffed veggies as an Egyptian cook. the things that store best when stuffed are firm vegetables: zucchini, eggplant, peppers, potatoes, and leaves. Avoid pre-stuffing tomatoes. When I prepare a dish like this, I stuff everything and line it up in the pot. The day I am cooking it (usually the next day) I let it sit on the counter to come to room temperature before I go ahead with the cooking process.

Megan, I have not tried doing it, my concern would be tomatoes, as they might leak water. But this is a type of dish that gets better with a day in the fridge, so I would suggest making the entire dish the day before and gently reheating it for the party.