Most people will answer that you cannot regulate propane twice. That is not correct in all cases. An RV primary pressure regulator, whether for a single propane bottle of two bottles, and whether manual or auto switch-over, regulates the pressure down to less that 0.5 PSI. That is normally measured with a manometer that measures in inches of water and 11 IW is normal pressure for RVs. If you put two regulators, regulating at 11 IW, in a row you will get no propane out of the second regulator.
On some fifth-wheel trailers there is a bottle on each side of the trailer (far apart). There is a long line connecting the two bottles, via regulators. In that situation the primary regulator, usually and auto-switching regulator) will be close to one propane bottle. That one is regulating at 11 IW (less than 0.5 PSI). The other tank, on the other side, will have a red high pressure regulator that regulates the high pressure from the bottle down to around 30 PSI before it enters the long crossover line. That just protects the long line from very high pressure. If you remove it everything "may" continue to work just fine...but it will be less safe and that long crossover line may not be designed to take the high pressure directly from the tank. The factory doesn't install that "high pressure regulator" in all their trailer by mistake!
Also, the excessive flow shutoff device does NOT reside inside the propane bottle. It, in fact, resides in the big nut on the "pigtail" line between the bottle and the regulator...the nut that attaches to the propane bottle outlet. That nut also has a plastic over temp. safety device (in case of fire). That device in designed to melt in the event of very high temperature and allow spring pressure to shut off the gas flow. The propane bottle itself has an overfill shut off, an over pressure relief valve and a check valve in the outlet that does not allow propane to exit the bottle unless a "pigtail' line nut is properly attached.