A typical LPG system will have a regulator on the propane bottle, the regulator is usually connected to a rubber hose, suitable for carrying lpg. If the burner/ appliance is more than 3' away from the gas bottle, I would recommend you run a small bore copper pipe to the appliance.
There's no need to use a fitting where the pipe enters the floor, but all fittings should be accessable. You need to check they don't leak.
In the UK a propane regulator will deliver gas at around 38 mbar.A butane regulator delivers at 27mbar. So most of the caravans are fitted with 6mm (1/4") diameter pipe. It's plenty big enough to run a small over, a hob, a fridge and a fire(furnace) .
It's standard practice to use compression fittings (with nuts and olives) on
caravan gas systems. When you have it all piped up, you should check all the joints on the system with a soapy solution . Any slight leak should show itself by bubbling. If you don't feel comfortable with the procedure, you should get a professional to either do the job for you or at least check over your work, and give it the thumbs up.
In the uk all gas fitters have to be corgi registered, and under go testing and retraining every five years. I've just passed my re assesments, so I'm covered for the next five years
If in doubt , get someone to do it for you.
Dave