All of my enclosures are display. I've been using Cypress mulch from Loews for a few years now without issue. They are $3.00 or less for a huge badge equal to the large Aspen bags.
The size of the pieces are not very consistent. The four bags I have now are very fine tiny pieces. The previous four to those were medium and large with a few XL thrown in for good measure. Sauzo called those sizes "prison shanks". But nothing to be alarmed at. None of the snakes have ever been stuck. The Cypress moves away from them as they crawl.
Lizzy among the "prison shanks".
My snakes are always in and out of their bowls spilling water, so humidity is a nonissue. If they do retreat to their skyhides for 10-14 days during shed, I just directly pour water evenly over a few areas to bump the humidity for shed.
It's very easy to work with.