Depends on the rc and what header/pipe will fit it. THS makes a lot of different pipes that will work with a 3.3 and you can use a lot of different headers to work with a THS pipe.
Shorter headers make more top RPM and less bottom end torque, longer headers are the opposite, more bottom end torque and less top rpm’s.
It all boils down to what will fit the application (unless you’re willing to modify). You wouldn’t want to install a pipe/header specifically designed for a Revo on a Tmaxx or Jato or 4Tec etc due to installation issues with pipe/header angle, hanger and stinger positions.