Factory Recovery is the best way to proceed with a second-hand laptop. It will start afresh with a new Windows installation, wiping everything that was on the hard drive and therefore getting rid of all the accumulated junk and old user accounts.
Factory recovery also installs all the drivers for that model so you've no need to worry about those, and you won't be prompted for the Windows Product Key at any stage either.
After recovery has completed, the "first run" setup process will prompt you to create an account name for yourself which will automatically have administrator status to create additional accounts later if you so wish.
Scroll down to page 26 of the User Guide, with the heading "Chapter 3 - Lenovo OneKey Recovery...