At the time of writing both AMD and Intel embrace the open source community. I would give the edge to AMD, though, if only slightly. Intel works great, but the scheduler (for E/P cores) is not as refined as on Windows 11. I heard there was recently a display issue, with Intel graphics, on Linux, too. That was a Kernel issue, and was quickly resolved. Just something to note. That being said, Intel networking is far better than it’s competition. Not just in driver support, but in actual capability.
As for size, it’s honestly personal preference. I wouldn’t go below 15 inches, usually leaning towards 16/17. Going smaller, I’d just wish I had a bigger display.