Scott, if you're booking the show, you have every right to inquire a worker's legitimacy. In fact it would be nice if all promoters looked into this, but that is a far fetched idea. As for the crowds, if you know your draw is going to be around 150-200 then absolutely it would be preferred to pack a smaller building, and it will make financial sense for you. A larger building will most likely cost more to book.
A cage is nice for special occasions, and if promoted right, will draw for you pretty well. However, they are costly, and unless you can find nearby feds that would be interested in renting one off of you, you would most likely be better off renting another promoters cage. Hope this helps!