A word mark protects the words themselves. If registration is granted, you can use the registered word mark any way you like and still have protection. This makes word marks the strongest trademark protection you can get (because the words are protected, it will not matter what your logo or someone else’s looks like).
For a stylized logo, the look and design of the logo is what’s protected. It includes any literal (text) and design elements of the logo. But if you change the logo, you risk losing some of your trademark protection. A stylized logo registration protects the exact design that was filed.
In the case of a stylized design mark, the trademark filed must exactly match the mark that appears on your goods/services.