Here's my take on heating snakes:

Ball pythons rarely bask in the sun. They are very nocturnal, and receive just about all their heat from areas that were warmed by the sun before nighttime, and from their borrowed burrows that they hide in during the day which provide a fairly comfortable ambient temperature during inactive times. I like belly heat with a warm ambient temperature.

Carpet pythons are definitely baskers, coming out to make use of bright warm sunlight. I prefer a CHE/sun lamp for daytime basking with a slightly cooler ambient temperature that varies with the season.

I tend to attempt to emulate such conditions as best I can for any species when designing an enclosure. The carpets that are in planted vivariums w/o belly heat (but have CHEs for basking spots) in fact make use of the shade and cooler ground to avoid heat when they're ready to find a cool spot for a while.

That said, I do currently use CHEs in some enclosures and flexwatt belly heat in others. All my carpet pythons seem to be doing extremely well.

I would not say that belly heat is important, but it is a perfectly fine choice. Just about all heating sources are proven to work very well with carpet pythons.

As far as temperatures go, these guys are pretty tolerant of a wide range, most exemplified by just taking a look at the seasonal averages of their native ranges. I let them experience ambients in the low/mid 80s during a peak of summer and mid 60s in winter.

Don't get sucked into following a single care sheet. Use your head, watch your animals, find out what works for you AND them. Reading animal behavior isn't that tricky if you spend some time with them.

I hope that helps.

P.S. I think the carpet python in the pic above is at least part coastal.