The P metallica you will keep like any other pokie. The ventilation holes in the enclosure is more to regulate the humidity. Stanley Schultz explains it very well in the following link.
people.ucalgary.ca/~schultz/spiders.html
I suggest you read it as it will answer a lot of your questions.
Regarding the A versicolor, Hendrijs (Hendrik) wrote a nice detailed report on how to construct an enclosure for Avics in general. Its an awesome read and if you follow it step by step you will not go wrong.
I can't remember the link to it but seeing as it is on the forum, use the search function and you will find it. The function will also help with a lot of the other questions you might want to ask.
Enjoy the hobby. And remember, not all rare T's are colourful, the more "common" ones sometimes have much more to offer.
That is my 2cents worth.
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