I'm on a late 2013 Retina Macbook Pro 15", Quad-core i7 @ 2GHz, 16gb of ram, 256gb PCIe SSD, Intel IRIS pro graphics. A pretty solid amount of computer, but OpenCPN is painfully slow. It's usable, but not pleasant.
OpenGL on or off doesn't seem to make much difference. Maybe slightly faster with OpenGL. I'd love to hear any solutions if you find them.
I reached out to the OpenCPN team via GitHub and they recommended I give the beta a try. I downloaded OpenCPN 3.3.2302 and it's probably 10x faster on my Mac. Still not buttery smooth scrolling (I still get better framerates playing high end games!) but much better than it was.
Betas are on the same download page, just scroll down a bit.