750w power supply

Solution
When I worked with the CX500 it did, you just line up the +2 pin until it looks like a proper 8pin, the put it in while holding both.
Its kinda hard to get at first, but once you get it youll see how to do it.
Generally no.
Doing so would limit compatibility with other components, it would not be a smart move.
If you want to avoid hanging cables (ie the +2) just get some sleeved extensions in the size you want, and leave the extra pins behind the motherboard.