#1
Are EMG's height adjustable or are they fixed like some pickups on schecter guitars?
#2
they're adjustable. also you dont have to worry about height so you can put them right up under the strings
#3
They're as adjustable in any given situation as any pickup of the same form factor.

They need to be adjusted quite close to the strings to get a decent signal, because they don't actually have super-strong magnets. Also, it means that you don't get string pull.

I have mine 1-2mm from the strings when they're fretted at the highest fret.
#4
^ Word.

People always comment on how close mine are
我会关闭我的耳朵,和我的心; 我会变成一个石头
"I will close my ears and my heart and I will be a stone"