Usually big tanks have regulators right at the valve.. HOWEVER...
You have been misinformed. The regulator is not much different than the one already on your motor home.. Just higher capacity is all.
The oil in the tank may separate, yes, that can happen. And if it does it can clog up the regulator (Not much else).. but that is as true of the motor home's mounted tank as it is the big one.
And what's more.. The big one it's more likely to separate inside the tank and stay there. EXCEPT WHEN THE TANK IS BEING REFILLED.
Which is why you turn the valve OFF when refilling.