17 R4, installing new SSD and would like clean install

I have my 990 Pro PCIe 4.0 NVMe M.2 SSD and am ready to make a clean install of windows (I got a virus a few weeks ago and would prefer to just start clean instead of clone).  I still have a few uncertainties after past assistance from other questions, reviewing other threads here and and watching Alienware YouTube videos.

First:  Can I use my existing SSD or HD drive to 'back up' and store my old items while I install my new SSD drive? (the recommendations I have seen were for either cloning or using a USB to back up the system).  What I would like to do is to save all the 'stuff' I want to keep on one of the current drives and then move them around after I have the clean install.  If this is safe, then is there a preferred drive to use for this?

Second:  I currently have my SSD in the SSD 3 slot and the SSD 2 is open.  Which slot is preferred for putting my new clean windows install and being the boot drive?

Thanks for the information and please feel free to suggest anything else you think I should know before undertaking this.  I am pretty novice here and have been taking videos of the information I am getting and saving it in case I make a mess of things and can't boot the computer back up (it has happened in the past).