High density hasn't been an issue for me lately on Ubuntu, I rarely use a touchpad, so I can't comment on that. GPU support is absolutely garbage on Mac OS in comparison, both from a compatability and performance perspective.

For you, but it's an issue.

Anyone who has used any Linux knows HiDPI or mixed DPI monitors are a massive issue on Linux. Even when you get your xrandr configured perfectly fine, disconnecting is a hassle. And that's completely ignoring apps, QT, GTK, etc all handle DPI differently. So you need a different config with DPI setting on each.

One of the best I've used is PopOS with the HiDPI daemon enabled. But even that has issues.

Even Windows can't deal properly with having a 4k laptop screen and a 2k monitor attached. Have to deal with weird text scaling issues and other weird scaling issues.

But MacOS can and does it beautifully.

My new Lenovo laptop touchpad works perfectly well (much better than my old XPS13). Running Pop_OS 20.04.

HiDPI is pretty good on a KDE desktop nowadays

Or good battery life