I've updated the results after the recent update, and the numbers are now very different. Metal now performs significantly better*, with up to 30% higher framerates. Additionally, the Metal version no longer had judder issues at 60fps, though it did have some issues at 30fps.
Unfortunately, OpenGL seems to have regressed. Framerates slightly below 60 are completely unplayable. If the framerate is at 58, for example, it's necessary to lock fps to 30 for the game to stay responsive.
*Sometimes the Metal version gets stuck in a weird state where it can't get above 80fps. This can be solved by going into the settings and toggling between different pixelation options.
| Resolution: 2560x1600 | GPU: Iris Plus 655 | Settings: Perfect | OpenGL (fps) | Metal (fps) |
| On Fishing Ship + No Pixelation + vsync | ~57 | 60 |
| On Fishing Ship + No Pixelation + no vsync | 57 | ~65 |
| On Fishing Ship + Default Pixelation + no vsync | ~230 | ~300 |
| Clump of Trees near Debt Guy + No Pixelation + vsync | ~57 | 60 |
| Clump of Trees near Debt Guy + No Pixelation + no vsync | 57 | ~60 |
| Clump of Trees near Debt Guy + Default Pixelation + no vsync | ~200 | ~250 |