The radio is capable of BLE and that is planned for the future, but Mesh runs on 6LoWPAN on the same radio.
Range is highly dependent on the conditions. If someone says the range is “15 feet through walls” do they mean concrete block walls or stone walls or wooden stud walls? Is there lots of interference from other radios? The best advice is that outdoors without obstructions, you can have very long range (there are several posts here about that) but indoors, it depends on lots of factors. The fact that Xenons act as repeaters to extend the range means that adding nodes can improve range.
My sit/stand desk at my day job in a typical commercial building has BLE so you can move it up/down for standing or sitting with an app. The app alerts me when I come back to my office to ask if I want to change from standing to sitting or vice-versa. During the day when everyone is here, the range is maybe 15-20 ft. At night, after everyone else has gone home, the range is maybe 40-50 ft. Nothing has physically moved but the amount of interference has gone down and the range has improved.