I'm not sure on your case questions, but on the h100i question.... it's a great CPU cooler but if you're not overclocking (or even if you're overclocking a bit) the air cooler that comes with the D3HP will be plenty cooling. It's not relying on just the case fans, it uses a fan on its heatsink in the same way the h100i uses fans on it's radiator, the biggest downside being this dumps the heat inside the case not outside (assuming the h100i was set up to be pushing air out) which is where your case fans come in, to replace that warmed air with fresh cool air.
Decent air coolers are almost as effective as 'All in one' water cooling solutions (though the h100i is particularly good) and have the advantage of reduced complexity with just a single fan (or, potentially two fans) that could fail instead of an AIO water cooler which will have fan(s) but will also have a pump and tubing, water that could become contaminated over time gunking up the radiator and so on.
If you were chasing a big overclock then the h100i would be a good option even for a novice (not as good as a full custom water loop but that's way harder and more expensive) but for most uses air cooling is the way to go (It's worth remembering that water cooling is just still air cooling, but using water to carry the heat a short distance allowing us a bigger radiator to disperse the heat)