There are two different device classes that physically are smart switch covers.
The go control that @OssotSromo mentioned will work well for smart bulbs because it does not Move the physical switch underneath, so it does not cut power to the bulbs.
The ecolink that you linked to will not work well for smart bulbs, because it does move the physical switch underneath. So it’s not really any different than having the original dumb switch as far as smart bulbs go. Unless you put it in a location on the wall where there is not a physical switch underneath it. Then it can work fine, but you have to put a childlock on the original switch to keep people from using it.
Back to your original question. This is a very good question and one that is frequently asked. 
We have two separate FAQs in the forum that should help. There are a lot of different devices that can be used. It just depends on what you need.
Start with this one: