Is parallels running the ARM windows preview emulating 64 bit X86 fast enough for anything practical? Can I play ten year old games?
Here's a bunch of reports people made for games: https://applesilicongames.com/
Based on peak performance at least I would assume yes.
Honestly I'd be a little bit worried if you couldn't considering just how expensive they are.
I should stress that my now slightly ageing laptop is much thicker than an Air, but it's also used to play modern games so that balances out.
Personally, for the price of an Air I could actually use I'd just get something cheap and a big PC setup.
It sounds like the things you care about are raw performance per £, and other factors are not important.
If that’s what you are looking for then the Air is not for you, but it doesn’t mean it’s expensive. It just means you don’t need the things it offers for the money.
If you do care about battery life, then the M1 Air is cheaper than the only comparable alternative - the M1 MacBook Pro.
Nobody else even makes anything comparable.
Actually not too bad - not good, but good enough for it to last long enough to write up lab data for 5 hours or so which is all I needed it to do. It's pretty diabolical in Linux, but I think that's partly my fault because I've not bothered to fettle with the power (not an unreasonable requirement given that the rest of the distro has been fiddled with)
If 5 hours will do for you, no need to spend the extra money.