They are plug and play with Alexa, but not with SmartThings.
The IFTTT channel works fine, but IFTTT does introduce additional lag. At my house, that’s a pretty consistent eight seconds, but it does vary from house to house.
If you do get lag in the 5 to 10 second range, that typically works fine for having lights come on at a particular time or for turning all the lights off.
If you use them with echo, you can group the Lutron lights in the same group as your smartthings-controlled lights, so Voice control works perfectly.
Where you will really notice the lag is if you want to have a SmartThings controlled motion sensor trigger a Lutron light to come on. You could find yourself standing there waiting for the lights to come on for a few seconds, which is annoying.
So that’s when people start looking at things like the raspberry pi local option.