I recently wrote the article. It is a reworking and update of my forum post, link, I made in July 2020.
Yes, you want to use the ACPI OSI string that is closest to the release date of the hardware. According to the ACPI standard, newer OSI strings should be backwards compatible, however, I have found that this is not always the case.
Not really. Linux distros, via the kernel, already follow the standard properly. Many hardware manufacturers see the ACPI standard more as a “guidance” instead of a standard. They often make “tweaks” that supposedly provide “performance” boosts, but instead break compatibility with the standard.
What the ACPI kernel parameters do is tell the kernel to “mimic” acpi calls as if they are coming from a different operating system. By using acpi_osi=Linux you are already telling the kernel to mimic the system that is already installed. Also, if memory serves, this kernel parameter has been depreciated.
I hope this helps to make things a little more clear. I go more into depth about this in the wiki article.