You have to use the new app to set up the V3 hub, but after that you can use either app or both. Many people are using both because of the issue you ran into: there are a number of features/devices which just aren’t supported in the new app. On the other hand, we do know that the classic app will be going away eventually, so if you’re starting from scratch you may not want to choose something that requires the classic app. That’s up to you.
The following thread describes the current known differences. (The thread title is a clickable link)
You should ask the support from Konnected for questions specific to that product.
