Propane Pipe in Generator Compartment - Can I Use?

Out of the box, no, neither. Here's why--

That propane line is already regulated down to 10-12lbs psi. Any BBQ or firepit you get has a regulator built onto the propane connection. It will not work, because 10-12psi is basically an empty tank to a regulator.
You will need to either get specifically an RV-Q for a bbq, or remove the regulators from whatever you buy and make a custom connections. Make sure when you're shopping for a bbq you get one with the regulator on the hose so you can remove it.