When Using Migration Assistant, Should User Names be the same on both Macs - or not?

I am giving my old iMac to another user. That user has a Mac Mini, running an older Mac OS.

I would like to make a SuperDuper! clone of his Mac Mini to an external hard drive, and use that, with Migration Assistant to move his applications, settings, and data to the iMac.

I have done a Clean Install of MacOS High Sierra on the iMac, and set up a new User Account on the iMac using the same User Name and password that he was using on the Mini.

So will Migration Assistant want to move his old user account from the Mini to the iMac - thus creating duplicate User Accounts on the iMac?

Or - will Migration Assistant just move his settings, data etc. to the User Account I have already created?

I am concerned that two duplicate accounts might cause issues? So maybe I should either change the User Account to a different User Name?

Or maybe I should run Migration Assistant from a second Admin Account created under my own name??

Thank you,