Relatively new to electric side of things. Just put a Novak Timbuk2 Wraith Edition in my Wraith, along with a JR9100T servo for steering (370 oz/in @ 6V). I think the Novak has a 2A internal BEC, but came with a 5A External BEC. How do I know if I need to run the external BEC? Everything seems to be working fine as is. Running an SMC 8000 mAh 20C 7.4v LiPo.

If everything is working like it should, you're good. Adding a BEC is simple enough, but it clutters up the inside.

I had a Novak Goat 3s system in my Losi Comp Crawler. It came with the BEC as well. The instructions stated to use the external BEC if using a 3s lipo. Check your manual and see if it's the same with your's. Added a mess to the wiring and a 2nd power switch.