This is my build https://au.pcpartpicker.com/list/LTkzvn, it will be the first time a build a pc with intent to overclock it so I am unsure as to how much extra wattage is needed.
750w is way more than necessary. A 550w will even support your system with CPU overclocking. A 650w power supply could support GPU overclocking aswell.
The RMx is a great power supply, you can save some money with a lower wattage variant.