BPs will push substrate aside to get to the heat of UTH if they want it, you just don't want to go too overboard or you are going to be digging substrate out of the water bowl constantly. For BPs I would not use eco earth personally, because they don't like things humid enough for it to stay damp, and it's going to stick to f/t rodents like crazy and get ingested. I would go with straight forest floor, a coco bark product such as coco blox, or a combo of those. Coco bark has much bigger chunks than coco fiber so it doesn't stick to rodents as bad, and if it does, you can pull off a chunk a lot easier than tons of tiny fibers.
How well each type of heating element works has to do with your climate, enclosure style, and whether or not you have a dedicated reptile room kept at a stable temperature in the right range. In a glass enclosure, you are likely going to need UTH for hot spot, and either RHP or CHE for ambient. I would avoid CHE unless you live in a really humid climate, and even then, you have to get an expensive pulse proportional thermostat for it, not an on/off thermostat. I have a dedicated reptile room in the high 70s, no BPs in glass enclosures, so just UTH only works well for me.