5s1p or 5s2p is going to depend on the cells used. Go with whichever one has the higher discharge rating. Other than that, there is no way to tell which is going to be better. The 1p pack should have slightly lower internal resistance, and fewer points of failure.

You're right on the mounts. The tekno uses the clutchbell. Without it, the motor is too far back from the spur to mesh. The RCM mount is for direct mesh between pinion and spur. The electri clutch thing from Tekno uses the nitro clutch, which will give you more slip when pegging the throttle from a stop. IMO, that is what the slipper is for ;).

As for the HV 6.5, I'll let someone else chime in. I personally don't think that is well suited for an e-revo, but we'll see what someone else has to say. Good luck with your build, and welcome to the forums!!!

J>