In regards to your tank, it is looking marvelous! With the rock and plants in you can move the heater down and it will be hidden. Also, as far as the filter intake tube, I believe you can take that center valve piece off, remove the bottom portion of the tube and put the intake pipe cover where the valve piece I suggested to take off is. It shortens the tube without cutting it, and it will still work just fine. That's what I did with my ME 400. If you leave it long like it is you're going to have problems once the fish get in there and start redecorating.
As far as stocking, yellow labs are beautiful. I think you should get a nice mix of different Mbuna. Pick a species group and start with that. See how you like them and rather than mix lake species think about the future and possibly getting a second tank down the road. If you are wanting a beautiful tank with happy fish then you probably shouldn't mix lakes.
Sent from my iPhone using Aquarium Advice