here's what i would do...
first, to answer your questions.
1. design for efficiency or looks. i like to do both. efficiency comes first, tho. i hate when a system just doesn't look right. my last system looked like a perfect grid, for the most part, all heads in a row. one thing to note, no system is ever perfect, you will never get a perfect design and in most if not all situations it's not a perfect square or rectangle.
2. 80 is a high psi but nothing i haven't seen. kiril is right, 60 is more around where you want to be. i would say more around 100 is where problems are inevitable, so you are kind of in the middle
3. i like to try to find the shortest length for the mainline, but your wire runs with it and you have to find a location for the controller and sometimes that's all the way around the house. shorter mainline can equal less potential problems. i would suggest a master valve as well, i usually put those in on any system larger than 2 or 3 zones, which is usually most systems, but using MP's uses less valves/zones
As far as design goes, i like to use mp's. I think you can get away with MP2000's on this system for sure, BUT i would suggest using the regular spray heads and not the press. regulated ones to get the distance. i would never recommend that, but in this situation is makes sense. i have found out that you simply can't adjust the nozzles down at all on a regular spray head, but if you put a press. regulated head in, you can take it down 25%. i love MP's, and on this system i would use MP2000's, 4 90's, 8 180's, and 3 360's (make a grid). this gives you a flow rate of 11.93 which is safe for a 5/8 meter, AND you can do it all on one zone. 15 MP's look cool when working all at once. longer run time, but you also have less zones, so it more or less cancels each other out. be sure to use a pressure regulated valve tho so you can have some control. keep in mind the 11.93 is rated for 40 psi, not 60 like your operating pressure would be (after back flow). hopefully you can turn the valve down and keep your distance, giving you a safe GPM