Currently my daughter has a Mac laptop that is about three or four years old and is struggling to run Adobe Premier effectively. I'm not sure exactly what chip is in it, but I know it is not a quad core
Late 2015 was when the MacBook Pro with the PCIe 3/4 "quad" bus was introduced. These have an NVMe 3/4 SSD to take advantage of the bus speed.
Older MBPs and other MacBooks like the Air have a PCIe 2 bus and corresponding SSD. Upgrading to a quadcore chip like the 970 EVO will not increase performance in these. You can install a larger one to increase storage capacity, however.
As far as I know, the 2015 iMac was the only one where Apple put a PCIe 2 chip in a quad bus. This did not change till the 2017 model.
If Adobe Premier is required, it does run better on the PC last I heard though Adobe has promised better Mac performance.
The 2012 i7 Quad Core Mini isn't a bad machine but its GPU isn't that great. An SSD drops in pretty easily if you follow the instructions. You do not want to leave a spinning hard drive in one.
I like the idea of a later MacBook Pro.
A 2018 Mini with a decent monitor, RAM and storage is more expensive than a 2017 iMac. I like 2017 iMac better—good monitor and better GPU unless you add eGPU to the Mini.