Confused at Motherboard Selection

[Vendetta1]

Okay, moving to next step which OS should I install, keeping in view I want to play games. I have following four choices, recommend me OS that is not a burden on my PC resources and will be efficient with them.

Windows 7 32-bit
Windows 7 64-bit
Windows 10 32-bit
Windows 10 64-bit

 

[PP Mguire]

Win 10 64bit.