Buy a mac to compil

So I am still a little confused. I am looking at getting a mac to export for mac like many of you but I don’t know what specs I need. The game we are making is finished on windows but I need to start testing on macs. I went to a mac store nearby and they have some used imacs https://www.expercom.com/browse_by_category.html?CATEGORY_ID=358. I

I saw the minimum recommendations of 8gb ram and the quad core but many of the imacs show nvidia but when I was at the store it was actually some iris graphics. Not sure what that is. How much video memory do you need?