I have the same problem on Windows 10. My friend at work too, different configuration. What even makes it worse, AE becomes completely unresponsive. Any solution?
I'm not sure what you are showing us. I'm not having that problem with OS X 10.11.6 even with a magnification factor of 400%. Screenshots of a cropped comp panel with no description of the workflow are not very helpful. There are issues with thick guide lines on some systems with some versions of AE but snapping should still jump to the nearest whole pixel.
I've seen the issue from a number of posters that on 4K and 5K screens, grids and guides are blurry. You can zoom in if you want it to be precise because it doesn't get blurrier or bigger when you zoom in.
Please file a bug report with Adobe.