you can get just as high from a small bong as a big one, although the size of the chamber can make a difference in how much smoke is conserved and a bigger bong will often be smoother allowing you to take bigger rips. bongs always filter out a little bit of the thc so its never quite as potent but its worth it because of how much smoother the hit is, the water cools it down a lot and filters out a lot of the carcinogens. i'm not sure why you would want to grind up your weed but if you are worried about the size of the bowlhole you can use a screen to keep anything from being sucked in. i bought a small handblown glass bong for myself a few months ago and i really like it, its easy to conceal is about the same size as a bubbeler but it holds a lot more water and takes smoother hits.