Having PF before distortion is like playing all kinds of intervals or chords on your guitar into a distortion box: anything but octaves, fifths and fourths will create an intermodulated mess. Placement of compressors, EQs and noise gates is not so critical (in relation to PF), and their placement in relation to distortion (and indeed each other) is another topic, so I will resist the urge to go into that here.
By the way, in relation to MF/TF placement, you might like to read my views on this in the topic ' Where do you run your modfactor in your signal chain?'
Cheers.
