When you upgrade from Windows 7 to Windows 10, as you suspected, the old Windows 7 files will all be preserved in and under C:\WINDOWS.OLD including updates, patches, and the original versions of those files.
The classical solution is to
1) Clone your Windows 7 PC before the update.
2) Upgrade to Windows 10. Run it for a few days to make sure it's stable (as your current hardware, if it was running 7, was not designed to 10).
3) Make sure you have the files and licenses you need to reinstall all your apps & data.
4) Do a clean reinstall of Windows 10 after erasing the hard drive where it was installed. Remnant DLLs and other files in an upgraded Windows can cause a world of grief, so this results in a stabler system.
5) Reinstall software, restore data.
No more Windows 7 updates and patches results in a much smaller system.