Qs about batteries in a e-Revo

[loa]

Hello,

Trying to get my hands on a revo roller so that I can start my conversion.

I'm also looking at Lipos, and I'm getting confused with the Cs and mAh combination.

First question: am I getting this right?:

A 4s 8000 Lipo rated at 10C should be roughly equivalent to a 4s 4000 Lipo rated at 20C.

They should have roughly the same amount of power, but would the runtimes be different?

Second question: would a 4s 8000 TrueRC Lipo (rated at 10C) be decent in a e-Revo? (planning to use a 9XL).

Third question: would I get the same power using two 2s 8000 Lipos instead of one 4s 8000 Lipo?

(Reason I ask is that I could use those 2s Lipos in my Rustler, whereas I couldn't do that with the 4s pack.)

Thanks a lot,

Loa