As other have pointed out, the type of track doesn't matter,tubular works as well as any other track with running conventional or command control.
I agree with others, check the other curve sections in the set, and look at the bottom , it should say what the diameter is, and likely it is O36. O31 was the standard diameter with O gauge tubular track that came with sets pre fast track. In any event, in the meantime you can use tubular.
With command control (lionchief , or really any of the command control systems) track voltage is constant (with Lionchief, 18v). If you are using the "wall wort" that came with the set that you plug into the wall, it puts out the right voltage. If you are using a standard transformer, you need to set the control on it so it is putting 18v out. Others have said 3/4 of the way, best way is if you have a meter, measure the voltage when it is hooked up across the outer rail/middle rail. The good news is if you do it 3/4 of the way, you likely aren't going to have too much voltage on the track and can adjust it as needed.
With lionchief your remote is talking directly to the engine, telling it what speed you want, rather than in conventional where you vary the voltage using the transformer handle. Lionchief + and LC 2.0 engines will run in conventional as well. If you put them on the track and don't address the remote to it, it will respond to the transformer handle the way any conventional engine did.
whether to use fast track or not is really a matter of taste. Tubular is a lot more rugged than fast track IMO, and doesn't have some of the quirks that fast track can have (if you have a bent pin in tubular, you can remove it and replace it relatively easily), also doesn't have the connecting tabs in the built in roadbed that can have a flaky connection. Fasttrack on the other hand looks more "real" than tubular, given the built in roadbed and the lower profile it has, but that really is up to what you want. Tubular of course looks more 'traditional"
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The rattle in the power section could be anything from a broken piece of plastic from the roadbed that is inside it,to a piece of metal tab. Unlikely to be anything earth shattering, prob would work fine if you use it.
