A 100w panel will do maybe 6amps mid-day, less earlier and later. 6 amps is two double lamps worth of Rv use--ie not a whole lot. It will certainly help (when the sun is out and you are in the open), but it is not a game changer between a 1000w and a 2000w gen IMO.
If you have a mix of gen/charger and solar, the idea is to do a fast charge with the gen in the morning and let the solar do the rest all day at its low amps before you hit the batts from supper through movies till bedtime and maybe some furnace at night.
That means the 2000w gen and a high amp charger for the short time gen part. It makes no sense to have a long low amp gen run and then a short period of solar at even lower amps.