How to achieve these tactics

I have found the AI to be lacking. If I am not attacking someone with my main character then all my followers just stand around. And if I change their targeting behaviour to "defend" they stand around until someone starts doing damage to me. Very frustrating.

In doing a small amount of reading, it seems the developers really want you to use the "tactical" camera for fights. This gives you complete control over every moment, but it feels really tedious. The experience improves slightly with practice I think, but overall I don't like having to control 4 characters individually.

Varric is always running into fights on me when I don't want him to. I love him as a follower for the banter, but man hes useless in a fight. Runs right up to a freaking dragon. I stopped resurrecting him and turned up his potion reserve so he would stop draining resources from the rest of the party during a fight.

I cannot speak about the "preferred" spell since I am just happy that my followers are looking in the right direction half the time. My hope would be that developers see the feedback (and these issues are pretty obvious) and patch a thing or two, but I'm not holding out for it...

Apparently, if you set ranged party members to follow themselves (e.g. set Varric to follow Varric) it makes them stay at max possible distance.

Sadly I have no solution for preferred abilities usage.