@Jeansoo Hmmm, you may have to delete that settings profile and start a new one. Try these steps:
1) Make sure The Sims 3 is closed
2) In WBG's Game Settings, select The Sims 3 from the menu, click Delete at the bottom, then close the window by pressing Ok
3) Boot up The Sims 3 in windowed mode and let it load to the main menu screen
4) Right-click the WBG system tray icon and click "Add Window (F3)". If nothing happens right away, press F3 in The Sims 3 window. You should see the window border disappear and a notification in the bottom right of the screen saying the game was added to WBG.
5) When you go to WBG's Game Settings now, it should hopefully look like below. If so, you should be able to enter the resolution, then click Apply:
https://i.imgur.com/ltZvLZm.jpg
