No artifacts or crashes that I know of. I have tested the mod with xEnviro myself.
ITC allows you to change the size, shape, scale, and color of X Plane's default clouds. Those functions don't work on xEnviro clouds. The same is true for some of the atmosphere settings.
Overall, there are no major consequences, apart from the fact that some of the "advertised" features of ITC may not work with xEnviro.
You are still able to change the intensity and color of night lighting, among other things.
In my testing, there's never been any stability issues. The only thing to consider is that some of the features of ITC may not fully work if you use xEnviro.
Give the mod a try, I hope you enjoy it. If not, that's totally fine too. 🙂