@mb1575,

If you are looking to have other devices perform an action when another is physically interacting with, your attention will need to be drawn toward the smart action features. From there, you can set one device to do something when another is interacted with, such as decreasing the brightness or toggling the light.

Creating a group will only allow the devices to be in sync with each other when sending commands to that specific group. Meaning that this has to be done through something that knows there is a group, such as the Kasa App or Third Party Integration. 

Having Devices stay in sync with each other is usually dependent on having devices talk directly to each other; which is why this is possible with a more advanced Zigbee network. As the matter protocol begins to be implemented into products, we may start to see more features such as this implemented into the Kasa and Tapo platforms

  @mb1575,

What you are trying to do can only be partially done in Smart Actions, as the triggers available for dimmers are only on/off; you wouldn't be able to change the brightness based off interacting with another switch.

For the groups feature, it allows you to control lights together so that they are in sync, however group commands cannot be triggered anywhere but through an app.