The differences in the overall finish will be noticed in depth and endurance. The higher the amount of solids the more expensive generally as well as more toxic. All single stage paints can be cleared over for thicker finish for color sanding and buffing but isn't necessary.
I'm curious about the clear coat. The paint I have from TCP Global says not to be clear coated. Not arguing, just asking. I have used Nason for the interior of my Barracuda and am pleased with the results.