I do cover IK in a few different tutorials, I can pull them up. I think most of the IK stuff I teach is within Live streams so I can link those when I find them and give you times when it is discussed in those streams. I would venture to say that most if not all constraints in Blender will not work. I’m not an expert in using Blender animations, but I believe you can “bake” stuff like that into animations then bring that into Unity.
It just depends what you’re using IK for. General IK is far more complex than humanoid IK. It can be done with generic rigs, but with humanoid rigs Unity does most of the heavy lifting for you. With generic rigs you essentially need to build an entire IK system from scratch since Unity has no idea how those rigs are supposed to operate.
