Yes, there are many species of apples. And most of them cross polinate. End of that discussion?
If OP wants to grow small apple tree bonsai it may make sense to grow small fruit trees no matter if it is called crabapple, malus sp or anything else. In any way it does not make sense to me to grow from seed. You will not know size of the fruits in many years. And maybe one day it turns out that it is growing huge fruits. Better to start with a tree you have seen the fruits on.
The tree in this video has grown from a compost pile close to my forrest. There are absolutelly no wild apple trees around, so it is most likelly that it grow from an eaten apple. Fruits is less than 10mm on this tree as well:
This is how many seed sown apples turn out, you just don't know before they start to bear fruits.