The moment it goes nuclear hypersonics, ballistic missiles and nuclear submarines will do the trick, nuclear bombers are really no longer a required part of the nuclear triad. If anything, China needs a stealth missile truck which the H-20 could do well in if procured in the right numbers.
For a bomber to work as a missile truck, it has to be able to carry huge amounts of payload.
Good examples of this would be the B-1B (34 tons), B-52 (32 tons) and Tu-160 (40 tons).
Bombers like the B-2 could only carry 18 tons of payload at most. B-21 would have an even lower (estimated) 13-15 tons of payload capacity, so I wouldn't refer both of them as viable missile trucks.
At present, China does not have any bombers that could play the missile truck role - the H-6 only has a payload capacity of around 9 tons, which is smallest among her strategic bomber peers.
To be frank, in the 1970s and 1980s, China did brush pass a bomber proposal which technically can be regarded as China's own (albeit smaller) missile truck bomber, i.e. Xi'an H-8, with a payload capacity of around 18-20 tons. Below is an illustration of the H-8 design variants by
@Deino.
Unfortunately, the proposal never progress beyond blueprints.
Therefore, in order for China's upcoming H-20 to work in the missile truck role, I think that her payload capacity must be larger than that of the B-2. That means either:
1. The bomb/missile bays have to be bigger (and hence, larger overall dimension for the H-20); or
2. Some of the payloads have to be carried underneath the wings of the H-20 (which would compromise its stealth capabilities).
For the second option, missiles with enhanced stealth capabilities like the YJ-98 and (rumored) HN-2000 can be considered. However, the solution would not be optimal for H-20's intended role as an all-round VLO stealth bomber.
If both options are not possible, the only way is to start the production run on the Xi'an H-8 at the same time as the H-20. But that would be rather unfeasible.
