I'm saying that from what we know, there are two separate general types - scramjet powered ones like DF-100, HAWC, Tsirkon with speeds of around mach 5 or to scramjet limits, and the DF-ZF, Avangard, and DARPA types which are boost glide whether boosted by MRBM boosters or ICBM boosters. These typically have far greater speeds depending on the booster.
There isn't an engine around at the moment except for China's sodramjet that could potentially be used on the second group. If there are any in the US and there are others in China, both are keeping them very quiet. The aim is to sustain the extremely high speeds of HGV and sustain them for much longer ranges than the already long ranges.
With China's recent hypersonic flight that flew within the atmosphere and around the earth, the Chinese may have such an engine or several propulsion solutions that allows a high hypersonic craft to sustain high speed throughout extremely long, intercontinental ranges. Something DF-ZF isn't doing unless it is also powered by sustained propulsion.
I've seen some references about sodramjet, but it has some inconsistencies.
In some sources, they claim that supposedly an aircraft with the sodramjet could orbit the Earth, which makes no sense.
The mechanism of the sodramjet system does not differ from the scramjet, which would be an air intake, a fuel injector (in most cases hydrogen) and a combustion chamber.
For the sodramjet/scramjet engine to work, the place where the aircraft or missile is flying must have air, outside the atmosphere it is impossible to start the engine due to the absence of air, exactly by this criterion, the scramjet works at altitudes level at 30-40 km, I still don't understand how a sodramjet will start the engine in Earth orbit when you have the air intake to make the engine run, injecting the fuel into the combustion chamber that mixed with the air creates the thrust at hypersonic speeds.
If there is any statement that the missile equipped with the sodramjet, but which has the aerodynamics of the HGV, being able to bounce according to the maneuverability of an HGV, I would say that the altitude of these jumps in the atmosphere would be at most 40 to 50 km, above that the air is starting to get thin.
Or going to the other extreme in the argument, as soon as the HGV was released from the IRBM/ICBM, it performed the jumps aerodynamically in the atmosphere, leaving and returning to the atmosphere, but losing speed, in the pre-terminal or terminal stage, as soon as the HGV was ready to dive into the target, the sodramjet would fire, which would cause the missile to gain speed, as the jumps into the atmosphere of an HGV take a toll on speed, an HGV can reach speeds above mach 20, but arrive at the target below mach 12.