I haven't tried any of these products yet. Do they pretty much all compare the same? Can p21s and souveran be used as one steps? Souveran seems too pricey. (the paste version)
I would probably look for some product other than one of the hi-grade carnaubas. You'll get better lifetime from it.
None of these products are "one step". The carnaubas you mention must be applied to a "perfected" surface. As jstn mentions, that product is a polish with minimal protection.
If you are trying to keep things simple, get the Poorboy's PwC AND the EX Sealant and then you'll have something! In addition, that will meet your 3 - 4 month requirement!