I'm not familiar with what better bee offers, but I build mine similar to the DE hive vent box. I like to make them the size of a medium, as it gives enough space to feed with a quart mason jar, and also gives room to put frames in for robbing out without causing fighting.
As far as the screen, DE hive screens them, but I removed it. I found with the screen, all kinds of bugs (earwigs, spiders, ants) will take up residence in them if the bees do not have access to patrol. I have never had bees draw comb in them either. Now I'm sure you can get them to if you cramp them enough.