My main complaint about the marketing landing page at https://cloud.google.com/appengine/ is that it doesn't contain any immediate information about the different environments. It does have a link to "Choosing the right Environment" but it's _waaay_ down below the fold. In general I wish Google Cloud product pages had their big "View Documentation" buttons up at the top next to the free trial button, instead of way down below the pricing section.
In addition, neither the "Choosing the right Environment" nor the "App Engine Standard Environment" docs linked at the bottom of the product page contain detailed information about the second-generation standard environment, which is frustrating. I do appreciate that the language-specific pages in the main docs link contain a short comparison that includes the beta environments, at least.
That said, the primary document comparing the environments (https://cloud.google.com/appengine/docs/the-appengine-enviro...) seems very out of date. For example, it mentions you should use the flexible environment if your app:
> Depends on other software, including operating system packages such as imagemagick, ffmpeg, libgit2, or others through apt-get.
However, the Node standard environment contains these three packages and more (https://cloud.google.com/appengine/docs/standard/nodejs/refe...).
There might be other nit-picks to be said, but really, my main criticism of the documentation is that trying to understand the split between "standard/flexible/second-generation standard" environments at first glance is tricky. I'm sure y'all have plans for this going forward as these environments come out of beta, so I'll hold off on whining too much more. Thanks for asking for further feedback, and for clarifying that the new PHP runtime is a second generation one.