This box, with a i7-6600U, routinely idles with the screen on at 5.5-6W with a current kernel (spending almost all of that in PC7 per powertop). Your ideas about Linux power management are just plain misinformed.
Tiny almost weightless (feels lighter than current-gen Macbook Air) laptop, and it runs between 10 to 11 hours on the battery when doing normal work (programming, mail, web, spreadsheets etc..) on wifi with pleasant screen brightness ...
Linux power management is fine today on modern hardware... (Powertop reports 5.2-5.5 watts)
Beyond that, run a current kernel (my measurements are on Fedora's 4.8.12 kernel). Also recognize that recent Intel SoCs have gotten a lot better at idle power draw. The "X1 Carbon" brand started with (I think) Ivy Bridge boards which obviously aren't going to perform like this.
I remember when Apple released it saying, 'no new features'. Just bug fixes and speed improvements.
We need one of those again.
I'm also a tiling WM fan. I found amethyst a resonable comprise when using macOS though.
Today's Dell and Lenovo laptops are good Linux dev machines. I've never had a problem with putting Linux one one, either my Dell Inspiron at work or my XPS at home. My old first gen carbon can even run FreeBSD-11 fine. Everything worked straight off with a stock kernel and the current linux-firmware package.
At one time, Macs were more cost effective for the specs you got. But with all the ram and SSD storage you can pack into modern laptops, they're really good dev machines.