Which type of Restore for wounded PC?

My Win 10 Insider system is analogous to a soldier shot in the leg: It cripples on, but it is not at fighting strength. I lost and restored my c: drive boot sector, Insider updates won't load, my logon presents duplicate accounts, System File Checker won't run to completion and more, almost all the problems are OS related......woe is me (or my PC)!
I know there are several ways to restore the system, but one of my crashes took out my pre-insider backups. I believe the System backups I have probably include the problems I'm fighting with.
I have hope: There is a clean 120GB SSD, available, and plenty of storage on other drives.
What I fear is that a clean OS install will be "unlinked" from my other important files and apps. I know they won't be deleted, but will I be able to mate them with the new OS? Could I put the OS (only) on the SSD and still communicate with the files on the old C: ?
How would you repair my installation? What version of Win 10 should I reinstall? Thanks for contributing to this discussion. I really don't know the best way to proceed right now.

Install only the SSD, leave all other hard drives disconnected. Boot the computer from a Windows 10 installation USB flash drive or DVD created with either the Media Creation Tool or from Microsoft Tech Bench. Do a clean install of Windows 10 to the blank SSD.

Once you have Windows reinstalled on the SSD, then reconnect your other hard drives. Make sure BIOS stays set to boot from the SSD.

If you don't like those results, you haven't wasted anything but time. Erase the SSD and you are back to where you started.

Thanks, I'll give that a try.