Schlage Lock, which app to use?

Hi, I’m new to the Smartthings world and just set up my first and only device, Schlage Connect. We downloaded and set it up with the “New” Smartthings app, but I was confused as to why it seemed to have very limited functionality, I was only really able to set up access codes and delete them. I was expecting to be able to set up temp codes over specific times. I watched a video to discover there was another app out there, the “Classic” which seemed to have so many more options.
I tried using the “Classic” and it looked like it wasn’t going to work with the setup we did with the “New” one. So, I guess my questions are:

  1. which should I use?
  2. Can I use both for the same device?
  3. If I can’t use both, do I need to set everything up again with the Classic to get the functionality I want?

Your best option is a paid app…

There is a free app but don’t believe you get the ability to set temp codes. And it has some bugs.