OCLP is great with the most recent OSs depending on your use case. But I don’t recommend it if you’re driving a computer really hard.
On something like an Octocore/12-core 4,1/5,1/6,1 Mac Pro with a ton of RAM or a recently dropped MacBook Pro with at least an Octocore and 16GB+ of RAM, going up to the latest OSs, even Sonoma 14.2.1 (14.4 is still right out, and even 14.3 has issues OCLP team is working on), then go for it.
We have now reached the point where my own testing shows the quadcores are struggling with anything past Monterey for maintaining the ever creeping resource demands we expect from modern heavy use. This is why I moved my MacBook Pro 2015 quadcore i7, 16GB RAM, dedicated GPU over to Linux. It was just working too hard on Ventura, let alone Sonoma. It ran just fine, but the fans were basically jet speed the entire time. Even after I opened up the back, cleaned it out, and even redid the thermal paste with Arctic MX-4. On Linux, of course, the fans still go jet speed if I’m doing heavy tasks, but that was true new (Apple always had an issue with fans running too hard under heavy load, going back many years).
I would basically say my current estimate is this for MacBooks, and it assumes SSD and max RAM.
Before 2007: Lightweight Linux, can do office tasks, but struggles with modern web even then. Older you go, less pleasant the experience.
2007-2008: 64bit CPUs, lightweight linux, perfectly usable daily driver for most tasks, but maybe not video over 1080P, light gaming equivalent to what you could have done 20 years ago (FPS, Minecraft, emulation of retro consoles) or more.
2009-2010: Sweet spot for lightweight linux. You’re likely to get annoyed by the quality of the screen before complaining about performance. OCLP is fine for macOS and basic use. What is the use case? Would not go over Monterey.
2011-2012: Linux flies, OCLP becomes truly viable, especially on better CPUs. OCLP on a 2011 i7 is very good. Get a max specced 2012, and OCLP is pretty great. Especially Monterey. Fans may be an issue.
2013-2015: Linux is just a total modern experience. OCLP is just a total modern experience, but beware of the fan issue. If it doesn’t annoy you, you’re good. It kept causing problems in my video calls. Noise suppression software wasn’t able to successfully avoid it bothering the other callers.
2016+: OCLP where needed is basically indistinguishable, or you’re running native macOS anyway.
Mac desktops are an entirely different set of experiences.
EDIT: Oh, another way to get those old unibodies to run faster is to remove the optical drive and put in an identical SSD and do striped RAID. I did that when I had a 2012 as my main machine, and it made a huge difference in speed. But be sure to back up regularly, as it does introduce more risk.