Stormer hobbies is fine so far as I know.
You will definately get plenty of runtime with a 5s2p setup- I havent managed to run my setup continuously until the lvc point since it tends to overheat the motor- have to take cooling down breaks.
In that case, a parallel harness is what you need- I would use either deans or traxxas plugs as the premade harnesses are easy to find, though I personally use 5.5mm god bullets > personal preference really any and all of the mentioned plugs will work fine, though I would replace the plugs on the lipos is they uses cheap deans copies instead of genuine ones.