Are these racks permanent, or are they easily removable?
No, it's not easily removable but could be taken off
fairly quickly with 2 people, it's heavy and the bolts in the front are tough to reach once installed.
Is it hard to "drop the top" with that thing on there?
No, you can still drop the top OK but the sunroof feature of my top is useless now. Just unlatch the front, raise it as high as possible, take the snaps loose and fold back as usual.