The general rule in RV's is 30 amps and below is 110, 50 amps and above is 220 (or 120/240 if you wish)
As for the generator... Most 120/240 generators have 3 outlets, the 4 pole twist lock is 240 volts and the standard 15 amp "Wall sockets" are wired one to each leg or one pair to each leg, in truth it matters not which you use, the "Wall socket" or the twist lock (properly wired with one specific lead left DISconnected) it's all the same to the gen-set.
However,,, Most gensets prefer (note, prefer is not the same as require) a balanced load, and your trailer is clearly NOT that.
Planned mod for my motor home is a box, likely in a storage compartment (Weatherproofed that way) with a 20 or 30 amp twist lock, 240 volt 4 prong, and a pair of standard 30 amp pigtail outlets.
That way I can use my "Vintage" (meaning older than the motor home) 30 amp "extension" cord to run stuff on the pignic table (That's not a typo) such as an electric grill or television or whatever. or I can plug in an extension cord to run my house... Should edison fail
(The house is wired for 30 amps, 240 volt, twist lock, as a back up,,,, Got tired of running a rats nest of extension cords, this is clean, neat and a single conneciton to run furnance, refrigerator, and freezer, along with other needed lights and such., Only thing not on the E-panel I might need is the centeral AC, I'll live w/o in a blackout)