Genset or solar depends upon whether you want to use the A/C or similar high load, long duration appliance.
If you want to use the Air Conditioner or to use other things that take significant electrical power for more than a few minutes, you will need a genset of at least 3 kw, preferrably 4 or 5 kw, capacity. This is a level 4 use.
Level 3 is for those who like a few comforts byt can get by without A/C. Microwave to heat things up a few minutes. Watch a DVD movie in the evening. Plenty of light when it gets dark. A smaller genset (1 or 2 kW) will do here to help keep the batteries charged. This is the 500 watt solar panel level. This level can often get by a day or two with Level 2 power capabilities using battery storage but will need a genset or more solar power for anything longer than a weekend.
Level 2 is for the highly conservative energy user. Occasional lights, water pump, maybe the furnace for a few minutes on a cold morning. 200 watts of solar (and 200 Amp Hr 12v
Battery) will usually keep this level in power but foul weather or excessive shade may require an occasional battery charging session on rare occastions.
Level 1 is the tent camper type, run only on dry cells in flashlights, level. Sometimes a 15 watt solar can be useful but mostly this is a disposable battery power level.
The question is for you to determine your preferred lifestyle in your RV.