Basic idea is only one reg per item like a stove.
If the grill is designed to be used straight off a tank, there will be a reg built into the grill and it should be connected BEFORE the RV reg. If the grill has not reg built in, then it can be used AFTER the RV reg.
TANK high pressure goes to reg and low pressure comes out to burner. But only once!
NOT high pressure to reg and connect to line to grill reg to comes out even lower?
Where to reduce the pressure this one time will depend on the grill and if it has a reg or not!
Why no RV year, make and floorplan on MY signature as we suggest for others?
I currently DO NOT have one!