Short answers:
IS there a converter on this rig: YES.
Where is it: Short answer: If your power distribution panel handles both 12 and 120 volts (Fuses and breakers) behind a common "last door" likely behind the panel, actually part of it.. If your fuse panel and breaker "box" are not the same box.. your guess is likely as good as mine.
How is the 120/240 volt separation handled.. Same exactly as it is in your house, do not worry about it, it is automatic. The only difference between wiring in a sticks and bricks and a 50 amp RV is the capacity (house is usually 150-250 amp, RV is only 50). It is all automatic, no need to be concerned.
But if you really must know, By the breaker panel, Same as the house.
What about when I plug into 30 amp using an adapter?
THe adapter sees to it all circuits get the proper power. You can not use any 240 volt stuff however. But then you do not have any to use.
What if you loose a neutral as I did in my house. Voltages on the legs go waco and damage to devices can happen.. EXACTLY WHAT HAPPENED AT MY HOUSE when that happened.
If you get the feeling I'm trying to say EXACTLY LIKE YOUR HOUSE.
you got it.