There could be other designs of flying wings, contrary to most people's belief B-2/B-21's shape is not the most optimal for stealth as it's lambda wing structure from the back forms converging trailing edges which under certain condition could form corner reflectors from the rear, this also is why B-21 only has a single large V shaped trailing edge instead of B-2's many V shaped trailing edge.
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This planform is the most optimal design for radar stealth, of course the intakes and exhaust could be further refined like the B-21 which has very low profile intakes effectively hidden when viewed from the front:
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Exhaust could take the form similar to this ADVENT proposal which has a S-duct not just in the intake engine but also in the exhaust to fully hide the engine. Along with a very low-profile exhaust that could blend into the trailing edge for maximum radar and IR stealth.
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All of these are new technologies for China and probably the rest of the world as well, hence the long development time H-20 is taking along with the fact that it has to be large enough to have sufficient range to strike CONUS, enough space to have atleast a crew of 4 and their amenities for the duration of the mission, carry enough cruise missiles to cause significant damage with a single sortie, probably also some technology onboard for it to fit into the next generation combat ecosystem.
Supersonic H-20 right now doesn't make sense; this isn't the 50s where flying at supersonic speed and high altitude could save you from SAMs and interceptors. Not to mention the range of such an aircraft is questionable, XB-70 was the closest thing we've got to sustained supersonic bomber and that thing had terrible range despite its massive size and the fact that it has 0 stealth what-so-ever. Even if you could make such an aircraft stealthy, you'll never reach the same level as even the B-21, you also now have to deal with massive IR signature from sustained supersonic cruise. Before someone says why not just have it cruise subsonically before doing a supersonic dash, back in the 50s when the XB-70 was designed that was exactly what they thought but they later found that optimising the aircraft for supersonic cruise was in fact more efficient than trying to do both. Optimising for extreme subsonic efficiency(required if you want intercontinental range) while still being able to go supersonic is extremely difficult and is what led to Tu-160 using heavy/non-stealthy variable wings and even today this is still the best if not the only solution.
Personally, I think H-20 will neither be a supersonic aircraft nor a B-2/B-21 style flying wing but something more unique in form and even more stealthy than the B-21 radar wise while also having a lower IR signature to evade modern long range EO sensors and future satellite based early warning systems.
