On my '14 20' FC I used the factory pre wire. It was #10, and goes from the front roof vent to the front electrical area under the bed (yours may be different). I used two, 100 watt Grape Solar panels from Costco, $140 each, delivered to my door. I used a Blue Sky MPPT charge controller, about $220. It does not need any additional control system. I drilled through the flange of the Fantastic Vent in the front to get the wire through the roof. I built my own mounting system, although now I would use the adhesive tape system which I believe is better. No roof holes.
I have changed out my batteries to two golf cart 6 volt batteries in series (from Costco). I replaced my Parallax converter/charger with a PD 4645 for better three stage charge regulation.
My system works well. I believe that about 200 watts of panel is the most that should be put through the factory pre wire, but it will handle that just fine with no serious loss of capacity. I also think that 200 watts of panel will be enough for most people's use in their RV.
There are no absolutes of course, each user has differing expectations and needs. I have been doing solar systems since 1995 and have done a number of them, including volunteer work for the Forest Service and their needs for remote solar systems. I tend to be a minimalist, that is I want good value for the money spent. Others don't mind spending a lot for a the very best system and are happy that way too. One size fits all solar is not for everyone, on either end of the financial or size, or equipment standpoint. There are differing opinions on which way to go. My self installed solar system cost about $700, the batteries $200 more and the PD converter/charger in the range of $200. I also installed a Tri Metric battery monitoring system for about $200. My labor is free to me of course.