#1
I'm about to change my pickups and I've noticed that the height of my pickups are all different. Starting from the bridge to the neck, the height of the pickups are descending (bridge being closer to strings) is this normal?
#2
Nothing to worry about, mate. Some people like the bridge pup closer to the strings for more crunch etc. I personally put the bridge pickup as close to the strings as possible and the neck & middle pups are almost all the way down because my pick usually hits them. You can easily adjust the pickup height and see what you prefer.
#3
You can adjust pickup height, so it's more of a personal choice.

What year was your 1570 made? The F08's have an issue with the pickup cavity route depth, which will restrict your choice of after market pickups. I bought a Dimarzio Crunch Lab & Liquifire set to go into my 1570, but they are too tall :P If yours is the same year, you'll be restricted to pups that are under 23-24mm tall. In my case, I just installed the Dimarzio set into my RGA121. I'm looking at BKP nailbombs for the 1570, the short leg versions are 22mm tall (according to BKP).
Fleet of MiJ Ibanez
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5150 III 50w & cabs
#4
Usually is about taste. A pickup closer to the strings provides a louder response, BUT it also decreases the sustain (particularly if it's made of a strong magnet). Also if you see you guitar from the side you will notice that the strings are higher in the bridge than in the neck, that's why the bridge pick up is higher. You can adjust them and try a little bit some times you get a nicer sound by changing the hight on either side of the pickup
#5
I believe mine is starting with F0 and ending with 7. I also went with tone zone, true velvet, air norton.

Ahhh I see, thanks for the information. I think I'll leave them as is, since it's a prestige. But I now know my options.