Pretty sure there are plenty of traditional x86 Linux laptops that have north of 12h battery life. System76 comes to mind (mandatory "System76 is just a Clevo wrapper" comment).
10W for video playback is a lot. 5w average for light workloads is not unrealistic... I think your perception of power consumption is a number of years out of date at this point.
After all, Apple claims 18 hours from a 54watt-hour battery - you really think nobody else can get within 2x of that?
My AMD Framework 13 running Fedora (an officially supported option: https://frame.work/linux ) also gets around that amount of battery life. And can run games surprisingly well.
Even when plugged in, AMD laptops are quite a bit slower than Macs. When unplugged, it's not even close.
Clevo is their ODM. They work with Clevo to put together a laptop, and Clevo gets the right to sell a Windows variant. Their version differs, particularly in firmware but also possibly in chips.