Windows 7 is so old that its drivers does not support USB 3.0, among other things.

So even if you use rufus and a genuine windows 7 iso to create a bootable usb windows 7 installer, it may not work on newer motherboard/hardware.    During the install you may run into issue of it asking you for cd/dvd containing new drivers.  Given that this is a pain, just install windows 10 with usb installer instead (though windows 7 requires a 4 gb stick and windows 10 needs 5+ gb)