Here is the scenery_packs.ini attached.
I don't know about the lack of engineering ..., it is just the way x-plane works :-) To make detailed and accurate scenery you put more and more objects, polygones, markings, textures on the tarmac and finally you have to buy a new video card as it happened with me. When I was making LBSF v2, my card was EVGA geforce 960 2Gb and with lower rendering options I was getting similar framerates, now with 980Ti I thought initially that would be able to max out everything, but it didn't work that way, especially because some of the rendering options depend on the cpu, not the gpu. Some of the options that I had to make compromise with were number of objects, resolution of the screen, shadows. Also noticed that noaa plugin even in clear weather causes sometimes 7-10 fps drop. Another framerate beast for me is w2xp scenery/library ( I use the osm only version). So, just try EPWA with lower screen resolution, it would be interesting what rate you'll get. Staying at 20 is dangerous. If you fly online when you start using ivao or vatsim plugin, add eventually weather and you will end up at 5.
scenery_packs.ini