In MCSM, the Wither Storm's later phases have a boom sound effect before the clusters get swept away into the debris ring. Also when the block clusters get ripped out of the ground, they are very fast.

There are suggestions for config options to increase the cluster speed already. Also I’m not really sure what you mean by a boom sound, but regardless I think the sounds that are already present are pretty good by themselves.

this is not mcsm this is cwsm his own thing it doesnt have to be 100% accurate

Maybe you could add it in the config.

But fast block clusters are better.