The "most common" are usually listed seperately from ones specific to the application. As far as more in depth explainations that those listed next to each option in --help, well my 'code of conduct' wrt that is "If I don't know what it does, it's likely I don't need it compiled in"
However, that does not really assist in answering your question... So with things such s PHP, you can read the overly in depth documentation provided on the website itself. You can usually find this is true with most
applications. Simply paruse the site's homepage a bit.
For general options though, as mentioned above, it's usually
listed at the top of the --help option, and IIRC is stated as "General Options"