ok here's my go on substrates and these are my "reviews" after having used some of the above mentioned.

cypress mulch - it "says" it holds humidity very well but i find that to be false cuz i was having to spray it several times a day just to maintain normal humidity, even more for higher humidity when my girl was in shed & i have 2 water dishes in there. so all that spraying = more intrusions to my girls home and she was not liking it one bit.
oh & watch out cuz pretty much all the cypress mulch that home depot & lowes carry also contain cedar.
cedar = maybe even . when i found that out i immediately switched to newspaper temporarily.
my opinion on that...i hope to never have to do it again. i absolutely hated it. you cannot spray paper. then i went to a 1/2 mulch, 1/2 newspaper (mulch on the warm side) to help with the humidity & it worked well enough.
now i'm using exo terra forest bark & my only 2 complaints on it are superficial in comparison to the others. theres the occasional splinters from handling it and poo is not very easily visible in it cuz it's pretty dark. (my snake has never gotten splinters though), in case anyone was thinking about that.
it's 100% fir bark and i only have to spray it once a day when my girl is in shed. with the bark the 2 water dishes can maintain normal daily humidity all by themselves but when my girl is in shed i bump it up by spraying the bark once a day and i keep a hand towel wet (but not dripping) on top of the screen.
so i'm loving the bark right now.