Well Mary and Bob I was being too generic regarding flare fittings, flares are a kind of compression fitting just a much more reliable type, got your nickel? (That is an HVACR technique). Type K Cu is not necessary in this application, propane
runs at 11” wc, that is less than 1/2 a psi, in my experience fully annealed type L is used in trailers. You can use K, ACR, or G but L is probably the most economical and approved for this use. Using a tubing bender you will be able to make the shortest 90, long sweep 90’s are used In HVACR to minimize pressure drop.