Switching to peat/coco substrate tips?

[JamesGSixx]

Salutations, friends! So I got a ball python and a red tail boa 4 weeks ago. My bp is housed in a wood glass enclosure, while my rtb is in a tub glass enclosure with paper towels as substrate. Their temperatures are spot on 90-95f on the hot side, 70-75f cold side. The humidity in both terrariums are pretty bad though ranging from 45% to 50%, this is when I don't mist. Both of them have humid hides filled with damp sphagnum moss to compensate but the problem is they're spending too much time on those hides instead of going to a regular hot/cold hide.

So I'm planning to change substrates to peat moss or coco fiber instead of paper towels. For the reason being so, I don't have to regularly mist, and I could take out the big humidity box that's taking up so much space and so it looks better and naturalistic.

However, My main concerns are

• Mold - I keep a bunch of tarantulas and sometimes their substrate which is coco fiber/peat moss, seems to get mold. These don't really affect tarantulas though, so it's no problem for them, not unless it's been sitting there for a very long time. Note that these tarantula enclosures have more ventilation than the snake's tub/terrarium and it's already getting mold so what more with the vents that the snakes have?
• Mites - Again, a common problem I face with my tarantula's enclosures. When the substrate is damp, they usually start showing up, Not an alarming number but just a few that you can notice them. I'm not sure if it's the kind of mites that can be harmful to snakes but they're not harmful to the tarantulas I own. They look like tiny white round slow moving mites I think they might be called "hitchhiker mites".
• Heating - Where do I put the heat mat? should it be at the bottom of the substrate or should it be in the middle?

I also want to know about the maintenance of having those two choices of substrate. What are the do's and don'ts? And what problems can I be faced with and how to avoid them? Thank you for taking up time to read this long post. Any advice or comments will be gladly appreciated!