I don't know that anyone can answer you specifically about july/august since this system is new and was not in place last year. That being said here is what we experienced in may....
Evening EMH...
MK-jam packed, not worth our time
Epcot-see above
AK-did not do
MGM-hardly anyone there and we road everything multiple times.
I think a lot of people including myself are waiting to find out, but my plan is to skip MK and Epcot as I am guessing they will be way too crowded. Night time parades and Illuminations are big draws to fill those parks at night. I am planning on doing AK for sure and maybe MGM.