RE: do small rubs equal small bucks?
We have footage of a spike rubbing a 6" tree under our stand last year.
Generally speaking, the big aggressive rubs are made by big aggressive deer. I didn't see these monster rubs up in Michigan because a "Big mature" buck wasn't living in any of the areas that I hunted.
I also personally believe that the larger the number of mature bucks in an area, the more agressive the sign. They just have more reason to be "pissed" and have a bit more rage pumping in their veins.
I believe bucks rub for multiple reasons. First, to leave a scent post. Second, to work agression out of their system (same thing we humans do at the gym by pumping iron), and building strong neck muscles that will be used when fighting. Third, to remove velvet (early in the season). And forth, because they have a rack on their heads and they need to do something with it (bordom). Why some bucks only rub small trees, while others rub large trees; is just dependent on the individual deer. They are all wired a little different just like humans!