I don't like Traxxas engines because they're too loud. They make acceptable power, though. The only real problems are the connecting rods, which seem for all the world to be made intentionally weak, and Traxxas fuel, which contains way too much oil because it's intended for use by noobs who tune their engines dangerously lean.

Plastic carbs are nice. They are more resistant to tuning changes caused by weather and engine temperature. I have plastic carbs on most of my engines and I haven't needed to replace any of them in years.

DO NOT BUY A USED NITRO RC AS YOUR FIRST NITRO. 95% of used nitro RCs have major problems that the former owner didn't want to fix. When you buy a used nitro RC, you're buying a major project that will probably be a money pit.