A 75g tank is the minimun for tangs. Yes they would be able to live with each other. A good rule of thumb is 1-2lbs of Live rock mer Gallon of aquarium water.
Think about adding a
sump,wet/dry or
refugium. These types of filtration will be the best choices for your tank over any powerfilter.
Start your tank of right by using
RO water from Avian, Windmill, or walmart. This will prevent unwanted minerals in your tank and less algea growth.
I'm olny telling you a little bit of onformation over starting a marine aquarium theres still much more to know.