Specifically I’m talking about writing software and compiling it. So between builds, there is plenty of time for the CPU to cool off. I don’t like waiting for a compile and want really quick turn around. But I love the MacBook Air form factor and I’ve used one for years until around 2018 when I settled for a MacBook Pro.
We can already see that the M1 isn’t throttling in the various Geekbench results so that gives me hope that this will work out for my purposes.
That's assuming you really aren't doing anything else but just writing code, and I mean... strictly just that.
Typically, I'd have a browser tab or two open. Maybe play some music, or make the computer read a book for me because... well, it is a computer after all.
Even if you don't do anything, Spotlight indexing and other services will still be running in the background. There is honestly a very good reason why the last few MacBook Air have throttled so badly. If CPU usage was kept low, you wouldn't see them throttle at all aside from when they are stressed, but this is not realistic with a desktop OS.
After 3 generations of a fanless MacBook (12"), and having had first-hand experience with how the iPad Pro, supposedly having a much less powerful chip, has thermal-throttled (plug it in to charge and start editing 40MP photos or play Fortnite at 120fps), I would never ever go for a MacBook without a fan. But maybe that's just me.