Sump design, Refugium?

I am in the planning phase of a new 75 gallon bare bottom tank. I will be using a 29 g tank that i already have as a sump.



I have done the research on the different types of sumps/refugiums, I am looking for advice on what i should put in the sump.



If you use a refugium with your BB what are the live contents and what purpose do they serve you?



DSB?



Miracle Mud?



Live Rock?



Plants?



Animals?