The use of formaldhyde has been discourged for the past few years - at least by quality RV mfgs. It does not take that long to clear the air - simply leave some windows open while the unit is not in use. If you go looking at rigs on a warm day, you will know the instant you get into one if its fromaldhyde free or not - you can also judge the amount of insulation.
As for Generators - most all trailers will have LPG generators as optional equipment. So if you want to use Gasoline then you will need to use one that is external to the unit. From other forums I have read where these LPG generators are still noisy, and very tempermantal with regards to fuel flow, have not read much about how much LPG they use. Most 5th wheels come with at least 2 30 or 40 lb tanks.
07 Chevy 2500HD 6.0L ,6 speed auto, 4x4, Blue Granite Metalic
05 Arctic Fox 22H