If you really want your options UI to be a separate window, apart from the regular Interface Options window, make sure you still add a panel to the regular window that has a button to open your addon's standalone options UI. Users nowadays expect options for addons to be in the Interface Options window, and are likely to get confused and/or post a comment about "the options are broken" rather than reading the addon's description to find the slash command they have to type to open the options.
