well, the 9918 is a 99A 18 NIMH capable controller. 18 NIMH = 21.6v, and 4s LiPo is 14.8v. Should be well within the operating range of that controller. Make sure you disable the built in BEC and use a receiver pack or UBEC though.
I have been runnign nitro for years, but this is my first real dip into electric other than the 18t. Sorry if I sound somewhat dumb, but on a good note my revo is running the RCM motor mount
Sure, if you look right up to the sticky at the top of this forum section titled "how to program your BK controller" it will have all the info you need. I've been running my 9920 on 4s for about 6 months now. You may want a fan on the ESC, other than that it's a great unit.