It depends on the tangs, for example yellow and purble tangs can not be in the same tank unless you add three to five
As far as other tangs as long as there not the same kind your ok ,example I added a sail fin and a nasa tang ,no problem there ,two different types of tangs
Now the yellow and purble should be added last as they are the nasty ones that tend to want to run the tank ,a soho is real nasty but pretty, once you add him in your done as he will not allow any other fish in tang or non tang
A don't suggest the blue hypo tang, there the first to get sick and they don't tend to do well in captivity