Thanks for playing - indeed the camera controls are a pain. I couldn't figure out how to adjust them. I asked on the Unity forum how to handle the new standard assets now. Hopefully they can help. :)
I tried the same thing while ago and I found this temporary solution if you want to code by yourself:
https://wiki.unity3d.com/index.php/MouseOrbitImproved
Or for a quicker result and to not invent again the cold water I used this super cool free asset:
https://assetstore.unity.com/packages/3d/characters/eazy-camera-102275
Hope this help :)