I don't use the streaming client, so I haven't checked. I believe that if eq2.ini is in the folder it should use it, but it's possible the streaming client doesn't honor it. Note that eq2.ini is only loaded when you start the game, so any changes you make while the game's running won't take effect until you exit and start the game again.
UI settings are just window locations and sizes and related settings like "Is the window's position locked?" or "Is it set for frame-and-titlebar, frame-only or no-frame?". The UI itself is independent of that, and loading UI settings won't replace the UI with a custom one.
"Hey! I'm not illiterate. I had a book once. ...could've used some ketchup though..."