The minis are usually one-half the volume of regular cupcake molds, and
even less than some of the larger muffin tins. Simply try measuring
the volume with water to compare between different pans.

As for uses, I use the mini tins for some brownie recipes. GRease the
wells well, and the metal surrounding each brownie makes the outside of
each brownie/muffin a bit more solid than if they were cut from a flat
pan, and hence less crumbs - - for receptions easier to hold while
eating and fewer crumbs on your carpet Same thing for cornbread,
or really, any cakes or muffins you like.
..
I have also cooked in quantity for after-church. Since I only have a
couple of mini pans, and several of the regular size, I just use the
regular size and fill them with half the batter I normally would.
But the wider flat results only work with some of the firmer recipes.
Liberally grease the pans so that, when cooled in the pan, you can turn
them over and taps them out. Digging with a flexible spatula, for me,
tends to break some of them.