Hey! Sorry you're running into this. It seems I am able to replicate the same exact lag you're experiencing by simply making the primary window wider than the screen resolution. I'm not sure the origin of the issue as when I check the CPU usage it drops when it is in this state. It might be something macOS is doing that is causing a delay in the render loop.
I will look into this over the next day or two and see what I can do. Thank you for reporting this.