I use a cookie ball scoop. So close to the size of a mini cupcake.
Purple, you asked about exact measurements. I don't have that but I like to have about 3 - 5 cups of cake scraps. (sometimes I freeze my scraps until I have enough to make a batch.) Then enough of your wet ingredient (peanut butter, icing, filling, cream whatever you like) to make a cookie dough like texture. So just play around with it. You really can't mess them up. Who knows you might just come up with the most delicious ones yet in your experiments!