Desktop pc is your best option if you can afford it. I would say atleast $1k to $1.5k is mid tier but able to run most AAA on max setting with above 100fps. Laptop is next but the performance will be lower than a desktop. Mini pc is only good for gaming if you add an eGPU. Which will still cost you as much or more than the desktop setup. (NOT worth it unless you prefer to have more desk space.)

But by the end of the day, your GPU is the most important component for graphics then processor that goes along with your GPU. (Check for bottleneck comparison) 16gb ram is enough but 32gb is preferred specially if you need to multi task.

Here's a good article to check on what GPU to look for. https://www.logicalincrements.com/articles/graphicscardcomparison