Way to increase the maximum zoom level

Your party members gain experience automatically, you don't need to take them with you. Even if they are just sitting around in camp, they still get the experience. So for the most part you can just take whoever you like.

There are some quests where you have no choice and are forced to take a certain party member. But as they are automatically leveled it does not really matter much. I would recommend to keep all your party members outfitted with some reasonable equipment for that reason.

You'll need to save your game right before you enter the Anvil of the Void room.

You will also need Shale in your party.

During the conversation options you'll have to either choose to side Branka or Caridin.

If you choose to side with Branka and save the Anvil you will need to kill Shale, which will stop you from completing "A Golem's memories". So save before you enter the room, pick one option, fight through the resulting in one achievement, then do the other. I would suggest that you choose to side with Branka first, killing both Caridin and Shale, then loading and continuing on since the subsequent unlocking of "A Golem's Memories" requires a trip back to camp, conversation options with Shale, and then a trip to the new area they unlock.