I don't have the Pure 7px so I can't comment on the first question. On the second question, when I first got my OPNs, the wires were too long in my case so the audi changed to shorter wires for me, but not until the next appointment, because she didn't have them in stock. So I assume that it should be easily changed, but you should probably tell her ahead of time so she can pre-order them if she doesn't have them. On my OPNs, the wire is permanently connected to the receiver, but plugs in and out of the HA. So it's not just the wire that was changed, because the wire comes with the receiver as one piece. That's probably why it's not as easy as replacing the wire, because the receive must be replaced as well.
It's weird that they didn't fit you with the same wire length in the first place. It could be that they didn't have 2 in stock so they went with one each for you, I don't know.
I don't know how far up your left HA sits. If it's really too far up that it's visible when looking from the front or the side, then it's probably too far up and should be replaced. But if it sits higher but still behind the ear and not visible from the front or side then that may be preferred over having it sit too low, which is why I changed to a shorter wire on both sides in my case. There are 2 mics on my OPN and my audi prefers the top mic (which picks up sound from the front) sit as high as possible behind the ear for better sound pick up.
HA wearer since the 1990's > Rexton Insite+ CIC (2011-2016) > Oticon OPN RITE (2016)
KHz 0.25...0.5...0.75...1.0...1.5...2.0...3.0...4.0... 6.0...8.0
Left ...10...10....10.....30.....70....75....80....95.. ..90....80
Right .25...30....40.....55.....75....85....90....90...1 00...100