For these older 12 inch 2017 models, the only thing you should really be using at this point in time is going to be Ventura as a shorter term option since its still supported until end of this year, or Sonoma/Sequoia via OpenCore legacy Patcher, since those still have 1.5 and 1.5 years of security and bugfix support respectively.. Older model 2015/2016 12" go straight to OCLP all the time, or Win11/Linux as alternatives discussed below.
Anything older than that at this point is not only considered a security hazard since it's by definition an unmaintained operating system connected to the Internet, but you're also gonna gain basically no favors running older operating systems on it. Even if you put your head in the sand and pretend security problems don't exist/will never be discovered/can be mitigated while remaining online, app support becomes a problem at some point, as well as just general support for more modern technologies like passkeys and such as a quick example, which are an incredibly good thing to have in 2025+. As far as performance stuff goes, majority of the performance stuff with these older models is basically just gonna come down to the fact that you're running a 7 year old platform that is not only very thermally constrained but also very power constrained, coupled with the fact that a lot of these units only shipped with eight gigs of system memory which wasn't amazing back in 2017 but anemic by 2025+ standards. Basically it's the machine that's gonna slow down the OS, not the other way around, and there's not too much you can do about that because of the fact that they are almost 10-year-old computers at the end of the day.
With that said, OCLP with Sonoma/Sequoia works pretty well with these units with no real major hiccups on them, plus assuming that the upcoming macOS version doesn't drop all Intel machines for good, OCLP will probably become available with that version as well. Alternatively, you can also get a patched version of Windows 11 to replace macOS altogether if you want longer support for something and there are a bunch of scripts available to basically completely remove all the stupid things like ads and stuff from windows, or as a really long-term solution and probably the best thing you can do for a lot of these older units, Linux. Linux will run on the rocks on the side of the road if there is a nerd with enough dedication to make that happen, and it's basically explicitly made to perform as best as it could on old hardware. You would be shocked how much life you can revitalize out of older units by just switching to Linux. There's even distros (variants) of it that are themed to look and feel a lot like MacOS, and since most people have work clothes that revolve around a web browser, Linux will basically support modern versions of chrome and Firefox until the end of time as well as receive a very consistent stream of updates and bug fixes and improvements and critically, security support.
All of these will definitely need some amount of work and time and patience and learning to get them working, such is the nature of the beast when you're trying to support computers that are nearly end of life. If you still have one of these 12 inch units and by the grace of God it hasn't encountered any of the numerous reliability things these units are known for, any of the above will absolutely keep one of these machines going and keep it in a state that is fit for usage in 2025+, or in the case of Linux, breathe a crazy amount of extra life into it barring hardware failures.