Yep, holes are easily drilled. I have an automatic watering system installed in them and it works great. I also modified some steel hog feeders to hold their feed, and that's attached to the side inside as well, keeps them from wasting too much.
Not sure yet what maximum capacity is, but I have about 50 in each right now and they do just fine. Before I add a new batch of weans to the group, I put some of their dirty bedding in the night before so the ones in the tank have a chance to get used to the scent. By the time I dump the new guys in, no one cares. I haven't had any issues with fights as long as I keep the sexes separated.