We used large taco tortillas and got 6 burritos. It will depend slightly on the size of your shell and how full you are comfortable stuffing.
Use GF tortillas (and GF options on linked recipes, when applicable) for a GF burrito.
For a vegan burrito:make sure your tortillas are vegan, follow the vegan cheese sauce and dry Ranch recipes linked, and use a vegan Ranch/sour cream.