Mixing cover is okay. Look at it like this...you are creating underwater condos. The sticks are like pup tents. Put a pile which measures 6'x6'x 4' and you have a Holiday Inn Express. Where would you stay? Mix some, segregate some. Have diversity of cover. As you plan it, think about travel routes for fish. Bass and bluegill don't like to travel across big distances of open water. Too risky. Build a highway with sticks, but create social gathering places with larger amounts of cover.
When you mix the two, you congregate different sizes of different species of fish, except largest bass. They like sharply defined cover, big tree trunk, big rock, that sort of thing, in fairly shallow water with quick access to deep water, off a point. That's perfect big bass cover.
Dense cover is for small fish. They like fairly shallow water. Fluffy cover should fill the water column, within three or feet of the surface.
Don't put cover in deepest water. Wasted space.

Teach a man to grow fish...
He can teach to catch fish...