Minor nit: a steam machine is running Proton. Which is wine, yes, but wine that Valve supports, wine with patches and changes (afaik, most of which get upstreamed to wine). On a Mac you're probably going to use CrossOver to package up wine.

Wine is wine, yes, but CodeWeavers is not Valve. Mac gaming is niche. The budgets involved are incomparable. Expect it to take weeks to months for hotfixes applied in days to Proton to filter through to CrossOver.

(This is my lived experience: HD2 patch 28th April broke wine compatibility, Proton had a hotfix in a day or two, CrossOver had a preview that partially fixed it May 11th and a release that fully fixed it June 9th; it was unplayable from April 28th to June 9th, longer if you count the stuttering issue that it suffered since March.)

The future of gaming on a Mac is also made less certain by the upcoming obsolescence of Rosetta. AFAICT Apple won't just pull it out completely, but they're clearly uninterested in supporting it long term, so over time the experience of trying to get x86 games to run on ARM Macs will worsen.

(I think I'll aim for a DIY PC build in 2027 in the hopes memory prices decline by then, but it's a faint hope!)

There's a lot less emulation to do though because it's still running on x86 and the same graphics chips so the main emulation are the wine system calls and proton that handles the graphics calls. Running the same on the M* chips you're switching entire architectures and there's just not the history there to support the work. Proton drastically improved Linux gaming performance and it's largely from Steam investing money in it to avoid being locked into Windows if Microsoft ever tried to wall off the Windows garden to demand a cut of every store on the OS like Apple does with iOS and friends.

This is true, though it's Proton, IIRC and Valve is much, much better at writing software around games than most are.

I wish that Apple would throw a few nickels that way; Apple Silicon is almost wasted without a decent games library. It would realistically be my only computer if that were the case.