Welcome and this is a good place to find out about the new GX550. You will find that a lot of people really like the, myself included, with some people having some minor gripes.
Good luck with your decision making.
I don't have the fixed running boards and should not have any clearance issues with the retractable one.
I will definitely be the first one to try it on a Luxury + if I get the part numbers needed for all of the mud guards and hardware.