Any of the platforms that have been talked about support Windows 7, the problem being is Windows 7 doesn't natively support the SATA or USB3 controllers and usually require initial drivers to install. Some Skylake boards the USB2 is also not supported natively via Windows 7 as it's done through a 3rd party controller. For my ARK dedicated box I had to install Windows 7 on another machine and use a damn PS/2 ball mouse to install drivers to it which was a serious pain in the ***. Forward Intel and AMD platforms will be even harder, as I mean Windows 7 is 7 years old currently. This is why I said before it's better to just get used to 10. The benefits outweigh the hassle anyways. Windows 10 is better suited for things like SSDs for starters.
For the previous board and PCI-E M.2, you don't have to disable SATA yourself it does it automatically. This happens because certain lanes are being utilized and isn't really an issue. PCI-E SSDs come with impressive figures on paper but the problem being real world performance doesn't really show at all. I was an early adopter of PCI-E SSDs just to see this myself and be able to tell people either/or. M.2 form factor is the way ahead for SSDs but IMO currently it's not cost effective to go PCI-E M.2 quite yet.
At this point you're adding unnecessary cost when the dollars can be better spent on something like a better GPU later IMO.