Best iMac Desktop for 4k video editing

Video editing and rendering requires a fast processor, plenty of RAM and lots of hard drive space. It is recommended that you have at least as much empty space as you have temporary files in your video project; I can easily amass 100 - 150 GB of temp. files while working on a one hour HD project, so I maintain a lot of empty space. As for RAM, you will want at least 16 GB minimum and the best processor (i7) you can afford. Aside from that, you will want to consider at 27" because you can buy it with the minimum RAM and add more RAM later (most recommended: macsales.com or Crucial) as you will save considerable money. And, you will want to check into editing software; iMovie (included) is awfully basic, but is a good way to start.

I have a MacBook Pro 2016 with Retina display and Touch Bar and recently played some 4K footage that I have from drones and cameras and the computer handled very well without any lag. I have not tried yet Premiere but I will. Maybe this might help you with your decision.

https://www.macworld.co.uk/feature/mac/best-mac-for-video-editing-2018-3449141/

Good Luck.