New builder need help with some stuff

[JT13]

What the difference between EPS and PCI-E?

 

Do extensions have a voltage difference or should I get full PSU cables? (Doing custom cables trying to anyways)

 

I have a MSI GTX 1080 Gaming X, And a HX850i  PSU, I want to know if I buy a 6 pin extension can I connect it to The 6+2 PSU cable? ( MSI GTX 1080 has a 8 pin and 6 Pin)

 

if i do get extensions what cables do I need I know I need 24 atx Pin, 8 pin, 6pin( if I can do it)

and a 8 pin for mobo