YF-100k is slightly uprated and has the gimbal system redesigned to allow this clustering (max is 7 for 5m). Since it's the next crew launcher they need mature technology not a completely novel design. Tooling is inherited from the CZ5.
Lots of interesting info here
The most important thing is this rocket actually targets dry mass margins and technologies beyond current Chinese state-of-the-art.
They have done a lot of optimisation for dry mass for this new rocket, which was something they really needed to work on to improve previous poor chinese rocket dry mass, incl:
- cold-pressurized gas cylinder compatible with liquid oxygen
- COPVs
- new pumps and and more compact TVC system
A very important step towards CZ-9.