I used Oak Plywood to build my cage that was a beardie cage and converted for a Ball Python. In the end I could have gone with pine because I sealed the heck out of it with a water-based sealant (4-5 coats on the inside). I even ended up using an oil-based stain because locally there were very few options in water based. WIth proper sealing/curing it is non-toxic. The key to it all is to allow appropriate times to cure for any stains used and also the sealant. If you seal it properly it is easy to clean and I used iron on edge veneer to clean up the edges and make staining sealing easier. It also gave a finished look.

The cage bottom for me was tiles I grouted in (for the beardie). Extremely easy to clean. Unfortunately I can't use a UTH with my setup because i converted it. I use a CHE and cypress substrate to keep humidity at proper levels. All temps good and humidity is perfect and holds for days. No issues with cleaning or hold buildup. I think the sealing (4-5 coats) makes the difference here.

If I were to make another plywood cage for a ball python or other snake I would create a PVC floor within the cage and keep an inch from the bottom of the plywood floor. This would allow for flex watt or UTH pad.