It can (or at least could the last time I tried it) detect installed games so far as the game is installed “properly” (meaning it has a “shortcut” .desktop file in share/applications). If it doesn’t, however, it’s merely a matter of adding a game “shortcut” config to Lutris (in case of games “properly” installed externally, or those installed in Steam, you only need to select the game from detected list). Wine installs can be a bit trickier; but if you want an “out-of-the-box” installation experience, it’d be easier to just make a new install and copy the settings folder from your previous install… I think that was your original question? Default usage of Lutris goes like this: you open the website, find the game you want to install, click on the relevant Install button and Lutris will run setup (you generally have to provide an installer or log into the client in case of Steam/GOG/etc.); then, the game will be added to Lutris and can be run from there or exported as a menu/desktop shortcut.
As for whether WoW runs well on Linux… I’ve played it quite a few years ago, and at the very least back then it worked quite well (it uses OpenGL so performance isn’t really any lower than on Windows… in fact, I’ve heard that it was a bit better on Linux). Then again, WoW has never been a particularly demanding game in the first place (which is generally the case with MMOs).