The "one hole" is for the "intake" to the pump..."probably" a 2" bulkhead in the 2 3/4" hole...(we haven't picked a pump yet.)
Why would you need more than that...?
There will be at least two (preferably 4) holes for the C/L "return" to tank outlets...
I agree that the 8 way can be a bit "much"...(or the 4-way with 3 way revs or 12 "ways" per tank)...especially in a smaller tank (under 200 gallons)
Too much "chaotic" flow goes nowhere...it just "jiggles" back and forth...I'd rather see "controled random flow" through 2-4 outlets that actually "moves" some water from one place to another...
Speaking of "moving" water -not sand...my suggestion would be to place the two "outlets" 6" to 8" >above< the floor of the tank..to keep from blowing sand, but still bringing oxygen rich water to the lower levels of the tank...
And the "intake" 6"to 8" below the surface to suck in oxygenated water to transfer down lower...
And then the additional two outlets in top front blowing down and back at the face of the rock to "wash" the rock (and corals)
By placing the first two outlets "behind" the rock work (but not "blocked") you will lift deitrus to be suspended in the water colum where the overflows can take it to the sump/skimmer/fuge...
The top front outlets will help in surface aggitation (again for oxygenation) and pushing suspended deitrus toward the overflows...
Running a "constant" flow (no O/M) will be fine from behind (preferable actually) but the top/front outlets should be on "Loc-Line" spreaders to be able to "adjust" them from time to time...
So the "back of the tank would look something like this..