Do they serve smaller donuts for those who have carb restricted diets? If so, are they limited to a small variety?

I think they have one GF donut but its the regular size. And they have Buttermilk bites which are donut hole sized. Other than those options its regular sized donuts

Yea gluten free is your best option, eat what you want leave the rest.

Not really. They do have donut holes but you have to special order them and there's a minimum quantity (2 dozen if I remember).