Do you really suspect that Linux would run as well as iOS? Isn't iOS optimized for the A17 and vice versa? It's out of my wheelhouse, but I suspect that this synergy is the only reason they seem so fast.
From the start, it was clear that a decent arm chip in a laptop is very usable. Paired with an SSD, and more ram, it would be killer.
MacOS would need some care to make it less heavy in terms of background consumption, but I don’t see that as being beyond Apple’s reach. Windows is a different matter, not sure what MS can bring to the table there.. The work being done right now in porting iOS applications to work on macOS clearly points to a strategy being developed.
Think it’s going to be an interesting couple of years.
Random example: https://www.macrumors.com/2018/11/01/2018-ipad-pro-benchmark...
I hook my 2018 MacBook Pro up to a 4K TV to present to a meeting and the battery goes down to about 35% after two hours.