I think I got it..... if you partition and start using a second, new ssd for storage, can you later install Windows 10 on it. If that is the question.... you can but you will lose all the items you stored.
If you want to use the new ssd as storage and later upgrade windows 7 on the other drive, it will still be able to see all the files and use all the programs on the second drive. That is if they were installed on windows 7.