There are many different kinds of virtual devices, you can take a look at what @taustin has done.
Just as an example, both a thermostat and a dimmer switch are multilevel devices. Not binary.
Prior to voice assistants, The type of use case you are describing was most typically done with a virtual dimmer, which gives you 100 different potential values (0 to 99). So you set the dimmer to 20, that means one thing, you set the dimmer to 30, that means something else.
You could do that with standard voice commands in Alexa, and you wouldn’t need an Alexa routine, you would just catch the value on the smartthings side. . But if you want to make the commands easier to remember, then you would have to use Alexa routines to get custom voice commands.
. But if you want to make the commands easier to remember, then you would have to use Alexa routines to get custom voice commands.