Right now I’m looking at 2 assets -
Generik IK - Unity Asset Store - The Best Assets for Game Making
Dynamic Bone - Unity Asset Store - The Best Assets for Game Making
From what I can see, these will let me the bones of characters and other mesh’s within the editor to create animations. Is that a what they do? I imagine I would have to have already rigged it in blender or etc, am I correct?
Not really. What those packages provide to a developer is the ability to add secondary motion to bones that are driven by animation applied to the other bones in a hierarchy. Additionally they provide IK solutions for set ups like a characters head looking at a specific point, or a hand locking to the surface of a wall, or feet planting to the side of a building (assassins creed, spider man), or pointing a bone hierarchy like arms/hands in the direction of the mouse cursor.
These IK set ups are commonly used with mecanim layers to override the base animations already set up on the character. So you can have the base layer animating the character walking in a tactical fashion while the override layer controls where the player points his weapon via IK setup.
Lastly - Unity has built in IK for the humanoid rig, but not for the generic rig, so rolling your own or using one of these asset packs allows developers to use IK controls on the generic rig and still take advantage of mecanim’s other features.