Hello and welcome, @micuat!
Thanks for pointing out the fact that docs are all over the place, this is a big problem that my GSoC mentor, @gohai, and I are currently working on solving. There’s new website that went live a few weeks ago that will be dedicated to Processing on the Pi: https://pi.processing.org where we will be centralizing content related to using P5 on the Pi.
I understand that currently we don’t have info pertaining to the opengl driver specifically. I created an issue in https://github.com/processing/processing-pi-website to capture that and we might be able to move that content over at some point soon.
Meanwhile, feel free to comment on the issue https://github.com/processing/processing-pi-website/issues/22 about what specifically was helpful to you and if there was something else you discovered that is not currently in the Wiki. The repo for the new site I believe is also open for PRs and contributions which are welcome!