Fold the rear seats down so you can access the latch mechanisms. Apply lubrication to the latch mechanisms. The pivot points are the components that allow the seat to fold. They are more difficult to access but not that bad.
I had the same creaking noise also. I sprayed the rear sway bar bushings, rear seat latches, and rear seat pivot points with IES silicone spray. I don’t know which area fixed it since I did them all at the same time, but I no longer have any creaking.
I have the SVE axle-backs with an MBRP X-pipe. It sounds good and has very little drone at lower non highway speeds (0-50 Mph). At 60+Mph it does drone a lot, especially if the road inclines. The drone also varies based on exhaust temperatures and weather conditions.