New day, new SSD, new Windows


I've just bought a Prime Day 500GB 980 Pro (£95!). I am going to add it to my system as my boot drive but... I want to know how to go about doing it so I don't mess everything up.

Current storage setup: 500GB 970 Evo boot/project/game drive; 2TB HDD storage drive
New setup: 500GB 980 Pro boot drive; 500GB 970 Evo project/game drive; 2TB HDD storage drive

I think the steps I'm going to need to do are:
  1. Back up everything and move all current files onto the HDD to make the transfers easier
  2. Make a Windows installation USB
  3. Remove the 970 Evo from the computer and put the 980 Pro in instead
  4. Install Windows
  5. Put the 970 Evo in the second SSD slot
  6. Format the 970 Evo
  7. Move all files back from the HDD onto the 970 Evo
Am I missing any steps? Is there anything crucial I've missed? Will there be problems putting the 970 back in before I format it and ending up with two SSDs both with Windows installed on them?

How do I set it up so, for instance, my main documents folder is on my secondary drive rather than the main one?