Just finishing a dual boot hack for video editing. Need help with scratch disk and hard drive setup!

I’ve got everything set up for the most part and really happy with my build and config. However, I’m thinking about buying brand new hard drives:

1 SATA III for Mac (500gb), 1 SATA III for Windows (500gb), and then 1 M.2 (1TB) to use as a shared scratch disk for all video editing purposes.

There may be other configurations that work but this is how I see it working best.

I’m using a Gigabyte z490 Vision G motherboard, which has a couple M.2 slots. I want to set this up for the best/fastest possible workflow for editing on both the Mac side and Windows side. I imagine that making the M.2 be the scaratch disk, while keeping the OS’s on the SATA SSDs will be the best possible thing to do.

Curious to know how you’d set up your scratch disk given these options? Additionally, is it possible to be able to have a shared hard drive that can act as a scratch disk for editing software from both my Mac side and and my Windows side?