nice lookin' tank.
You will find that there are many schools of thought on the different types of fish one "should" keep together. You will find people on the extremes: from one kind of fish per tank, to anything goes. From tankmates only from the same source, to, again, anything goes. ---and everything in between.
I will leave that can of worms for someone else.
As for stocking, many people use "overcrowding" in African cichlids tanks to help offset normal aggression and territorial issues. It seems to work well in many situations. Of course, filtration then becomes another story.