your 720p tv will still have overscanning unless it has a 1:1 pixel setting, which most 720p tvs don't have this capability, so there will be some degree of overscanning. This isn't a problem with your DVD but with your tv. That is why dvda has the safe area markings on the menu screen so you can plan out your menu highlights to compensate for any overscanning.

If you are adding the text in dvda then you don't need to do this, but i prefer to have the text created at the same time i create the menu video so i can have fade in effects etc