1) You need to change the animation setup - the 3D quickstart and playground series use the legacy animation system (i.e.
Animation component).
If you use
Animator components, you need to change to using Mecanim animations, they're e.g. used by the
2D quickstart or
3D action RPG series.
Generally, you'll most likely always need to adjust the animation setup to match the model you're using for a combatant, i.e. beside using the matching animation system, you also need to set up the animations depending on how they are available.
Also, for Mecanim animations I'd recommend to not use auto animations as it's done in legacy animations, and rather forward the movement speed to the animator controller, using a blend tree for idle/movement animations (e.g. as in the other tutorials).
2) The first combatant you add to the group will automatically become the player. Afterwards, you can control this either via having the player change the group via a menu screen (
Group menu part, e.g. here
an example from the 3D playground series), or via schematic nodes.
There are nodes to change the player, or e.g. set a locked field leader to always have the same combatant be the player outside of battle. Or use a non-battle player as e.g. in Pokemon, the
2D grid battle series uses such a setup.
3) Gave it a quick test and works fine on my end (3D playground project) - might be a broken NavMesh on your end. Try rebaking the NavMesh in the
World scene.