i7 vs i5 processor for Adobe Premiere

I would recommend skipping the MacBook Air entirely for video editing: Its CPU is far weaker than either of the two Windows options (all Y-series CPUs are only dual-core and extremely low sustainable CPU clock speeds, versus the eighth-generation U-series CPUs that are at least quad-core and modest sustainable clock speeds, and the 8750H is a 6-core CPU), and it does not have a GPU that's at all suitable for Premiere Pro. In fact, that MacBook Air relies solely on its extremely weak integrated Intel HD or UHD Graphics that's not even at GT2 level - it has too few processing units to even enable OpenCL or Metal GPU acceleration at all! As a result, Premiere will be permanently locked to the software-only mode for renders, which would then fall back entirely to the underpowered CPU for those tasks. This will, in turn, cause the exports, especially those with even a single nominally GPU-accelerated effect, to be slowed down substantially. As a matter of fact, it is barely suitable for even 720p, let alone 4k, video work.

And that's not to mention that there have been more issues (at least in these forums) between Adobe and Apple than between Adobe and Microsoft when it comes to program stability.

Between the other two options, go with the 8750H. You will want the most powerful CPU you can afford if you're planning to work with 4k/60 videos.