Many of us use voice with SmartThings. Some people don’t. But if you like voice there are a lot of choices out there. There is an official echo/smartthings integration which works very well. Some people use yonomi with echo to get additional devices. There is also a very good android implementation based on a combination of Tasker and sharpTools. You’ll find all of these and more discussed in the voice command solutions thread:
There’s also a popular community-built Alexa skill integration called AskAlexa which allows for custom utterances and query capability. The only problem is you have to be pretty technical to set it up and run it.
As far as what devices, I use mine mostly for control of lights, my home entertainment set up, and my Door lock. But smartthings is extremely flexible in which devices it can work with, so you’ll find a lot of variation in brands and models.