One good thing about making your own sausage is you have some latitude to do your own thing.
Snack sticks are usually smaller diameter, sheep casings casing are a good choice if you are wanting a natural casing.
Brats and landsjaeger would be about right in a hog casing.
Bologna can go in a fibrous casing, but is not a natural casing.
Hog casings and sheep casings will vary a bit in size. A lot of casing suppliers will gauge them so you know what the size you are buying. Casing size consistency is probably more important for commercial processors looking for uniform weight and size for their product packaging.