Where are you located? Climate has an influence in this.
How big of a run are you planning? Chickens don't understand words like coop spaced or run space, they just understand if they have the room they need when they need it. That's part of why your climate is important, if the run is not available because of weather it doesn't count.
What breeds and sizes are you getting? Bantams don't need as much room as full sized fowl.
I totally agree with simple. You need to make it convenient for you to manage it. Simple to build is a huge benefit. You are important in this. Cute you can manage with paint and other stuff. That has nothing to so with size, just your imagination. With paint and maybe cut-outs you can turn most coops into Tinkerbells' castle, a field of flowers, or about anything else you can imagine. You say Tink doesn't have a castle. Well, design her one. Have fun doing it.