If you choose any content in your signature template, you can add, remove or change the Styles it is connected to.
You can do so by clicking on the Stylize button and choose which operation you want to perform.
Connect Styles works exactly as you expected. If the content already has some styles mapped, they will be replaced by the choice you make and confirm in this window. If it doesn't have any styles mapped yet, your choice will be added.
Disconnect Styles is pretty straightforward. If you choose this option, just click which specific styles you wish to be de-mapped from the content you have chosen. So you can keep e.g. the Font family and Font size but remove the color style.
The options in the pop-up window mirror the choices available in the Styles window.
Launch a guided tutorial under this link.