Lookat Direction by AddTorque?

I have a rigidbody character spinning only around Y.

I need it to be able to set direction in 2 different ways / different player modes, using AddTorque:

A) Look at Target over time

B) Look at Direction over time (Direction = normalized Vector 3, like the normal returned from a raycast hit)

I can do either with different code, but I want to use the same code for both as much as possible, to have the same behavior in terms of smoothing etc.

I have settled on a well functioning code for A) Look at Target.

Now I cannot for the love of god get my head around how to adapt it to not spin, but focus in a direction, as B)

Here's the code I use for A), which I really like the feel of, and need to adapt to a B) mode..

     float rotationSpeed = 10f;
     public GameObject targetObject;
     Rigidbody rb;
     void Start()
     {
         rb = GetComponent<Rigidbody>();
     }
 
     void FixedUpdate()
     {
         Vector3 targetPosition = targetObject.transform.position;
         Vector3 inverseVect = transform.InverseTransformPoint(targetPosition);
         float rotationAngle = Mathf.Atan2(inverseVect.x, inverseVect.z) * Mathf.Rad2Deg;
         Vector3 rotationVelocity = (Vector3.up * rotationAngle) * rotationSpeed * Time.deltaTime;
         Vector3 deltavel = (rotationVelocity - rb.angularVelocity);
         rb.AddTorque(deltavel, ForceMode.Impulse);
 }