correct way to emulate servo motor (position, velocity, intvelocity...)

I write some simulation code that should mimic the robot fish swimming with servo motor
when I have ` https://mujoco.readthedocs.io/en/latest/XMLreference.html?highlight=intvelocity#actuator-intvelocity
**What is the proper way to emulate the servo motor?**

p.s for now i use `` with the high kp gain that I am not sure how to tune appart from trial and error.