Thor159 :
Is there only 1 motherboard H270 which is overclockable?
CPU's are overclockable, not MOBO's.
MOBOs only gives the option to do that or no. In that scenario, only Z170 or Z270 MOBOs can overclock their unlocked CPU's properly. Any other B250,H270, etc... Can't.
And that "H270" is it's chipset, with that there are lot of MOBOS models that use the same chipset. They all have the same chipset but can vary on aspects like size, SATA ports, etc...
Basically, what you wanna do is choose a chipset to your CPU and then choose the model with the matching features you want to get.
SLI and CrossFire is the capability to run two GPU's simultaneously being either NVIDIA or AMD respectively. That
in theory improves the gaming performance as there'll be two GPUs to process the game. In reality isn't that simple as the game has to be optimized to use that and many games aren't, so as a general rule 1 strong GPU is better than two weaker ones.
These are the mobos you wanna look for:
http://pcpartpicker.com/products/motherboard/#L=4&u=1&sort=d6&c=120,121,122,119
I believe all newer mobo's have more than 4 SATA ( It's the cable slot connection for it, "just like USB" ) ports, so as long as you pick a SATA HDD or SSD you can use more than 4 at the same time.