The reptile sand and reptile carpet have issues that I don't think will do your boa any good and will drive you nuts as a keeper. I'd never use either for our boas.

For ours we use either straight up fine shred aspen or for the bigger, heavier boa an aspen/cypress mulch mix we do ourselves - 2/3 cypress to 1/3 aspen. The cypress mulch holds humidity and will stand up under the heavy weight of a bigger boa. The aspen adds softness (and I like the look of the dark and light substrates). The aspen is fine alone but once the boa gets heavier it tends to compress so much that it can make underbelly heat be a bit less efficient. Mix the two of them and you get the best of both.