I just finished prepping Sterilite tubs as temporary quarantine/grow-out tubs here in Dallas too, and the summer is definitely killer so dial them in before you get the snakes!
I'm using Ultratherm UTHs (well, one is on a spare ZooMed I had laying around but I don't really recommend that) and AcuRites to measure temp and humidity. I put a row of air holes around each side and a few rows in the lid (slightly different tubs than what you posted). The ambient temps want to hover around 80, and the humidity with a water bowl inside easily holds in the upper 60s and as high as 72... two of the tubs are for kingsnakes, so for them I had to put in even more air holes and then put a fan near them to get the humidity lower with more air circulation. So based on that, they'll be super easy to make work for ball pythons.
Edited to add: Also, I'm using paper towels as substrate because of quarantine and still got those initial numbers for humidity. I feel like cypress mulch would make the humidity spike way higher than you want, but you can try putting the mulch in when it's not super wet right out of the bag and see what happens.
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