Symmetric and asymmetric quad frame parameters

I briefly looked through mixer (.mix) files for quads and all of them seem to be for fully symmetric frames.
What about quad frames like TBS Discovery and IRIS? Do they need a specific mixer or generic Quad X with the right PID coefficients will work well ?

I have a Reptile-500 quad frame from Hobbyking that looks similar to TBS Discovery frame (i.e. angle between two front arms is wider than angle between the back arms). Is there any benefit in changing generic Quad X mixer for this frame ?
Is there any difference between QGC airframe options “Generic Quad X” and “TBS Discovery” other than PID coefficients?