Yes, some kind of bottom bracket hole is good. Just to drill a small hole at the lowest point is a good thing.

As for vent holes on the frame, you can find superb frames with them and some where the builder decided to close them. It's just a matter of the builder's aesthetic -- some consider it a natural part of the bike, others like to close them up. Consider that it's just a little bit of putty or filler under the paint, and you'll realize that whether it's plugged or not is relatively irrelevant. It's the last reason to discriminate for or against any particular frame.