More details, options, setup, etc. is pretty much what I'm saying. Not an exhaustive list of uses, just a casual observation. Offhand, I can look up and to the right as I am typing this, and I see three dots, although vertical, does bring up more details, as you stated, on my mobile google browser. So what I mean to say is thank you for adding to my statement.The vast majority of the time that i see "..." it means more detail. I have NEVER seen it used as an options or setup button with the exception of some installers where "..." is next to filepath entries and means to manually select the filepath. Options or setup buttons are usually either a gear or wrench icon.
I have no idea what programs you are using that have "..." as the options/setup button.