There are 4 different configurations:

Variant 1: RWS Recoil + Tracers
Variant 2: Vanilla Recoil + Tracers
Variant 3: RWS Recoil + No Tracers
Variant 4: Vanilla Recoil + No Tracers

I recommend using the RWS recoil versions together with the RWS recoil versions of the RDE 4.0.1 patch for optimal playability. If you use the versions with Vanilla recoil, also.