Meh. I bailed out of the Mac ecosystem last year, as my mid-2012 retina Macbook was finally getting too creaky, and the latest Mac hardware was a regression in many respects, while simultaneously utterly unaffordable. I'm now dual-booting Ubuntu/Windows 10 on a Dell XPS 15". What this experience has taught me is that computing in 2019 basically sucks. The problems with 2000-era Linux, as described in the article, are…
I have a 4k dell xps 13 and a 2k monitor. I have this script set up to run on boot.
https://gist.github.com/kn100/7193667d393fcf34d4d5c6c359a695...
What this does is it forces your internal display to run at exactly quarter resolution (ie 1600x900), and adds your second display at its native resolution to the setup. Since the panel is running at a multiple of its native resolution, it still looks fine, if not quite as pixel perfect. This has the nice side effect of making the laptop feel a bit faster since it's driving a quarter of the pixels it usually has to drive. This makes the monitor panel do the scaling too, which is nice. With this setup, both displays will be running at a roughly similar DPI which will make scaling issues... a non issue!
I hope this helps.