should I use migration assistant on my new iMac or do a clean transfer

I've done both. If you wish a pure, clean start with the new Mac don't use MA. If you want to transfer apps, data and settings use MA.

It's a personal choice.

I used MA to setup my new iMAC from my old MacBook Pro and I want to change the system name.

What are the steps to do this?

TIA.

+1