If they are going to put those huge U-VLS cells on 054B, I don't see any reason why it should still be using HHQ-16. That would be a terribly inefficient space usage.
Not really. If the missiles are hot launched, it will be a canister within a canister so part of the U-VLS space is used for exhaust release. This replaces the exhaust release and transfer channel used in the AJK-16 VLS, but this channel uses up space anyway in its own way. So this is an equal exchange. The channel for the extra VLS size.
If you want to use cold launch, like the land variant of HQ-16, then it will only be a single canister and there's plenty of space around the missile. However cold launch dictates that you need a gas bottle to throw the missile into the air and that requires that you lengthen the VLS.
For whatever reason PLAN has decided to use hot launch for the HHQ-16, I don't know why, they will stick to their choice nonetheless despite the land variant being cold launched. Should note the Russians are using cold launch for their Shtil VLS.
For the 054B its likely you will use a new shortened version of U-VLS. This let's you save space and weight for a smaller ship.
Please note the YU-8 ASROC will have to be hot launched just as it is on the AJK-16 VLS.