What size objects can be created from collision of two asteroids? Does collision of two asteroids necessarily create only very small objects? (and how big is it "very small"?)

I am especially interested about collision of two asteroids with similar orbits (and thus relatively small difference of the speed vectors in the moment of collision).

Can such a collision create big (say 1km, or maybe 100m) objects?

Is it in this case likely that a created object would have something like a comet tail consisting of dust and small objects (probably gravitionally attracted to the resulting asteroid remnant)?
Since planets are forming from asteroid collisions, I would say those collisions won't necessarily create small objects.

Imagine throwing a snowball against a window.

If you throw it lightly, some snow will stick to the window and increase the mass of it (at least until it melts away) and the rest of the snowball will be scattered everywhere around but won't stick to the window.

If you throw the snowball too hard, the window will break, resulting in even more tiny pieces. But still, some snow will stick to some pieces of glass.

That's exactly what happens on asteroid impacts and depends on the speed, mass and structure of each asteroid.

The size of those debris should reach from microscopic dust up to gigantic rocks with several kilometer wide diameter.