How do I make clouds spawn at A to destroy at B?

Hey, I'm making a 2d game with some clouds passing by from right to left. There's two types, big and small clouds where the bigger ones goes faster and the smaller ones goes slower (t$$anonymous$$s to simulate dept and distance). As it is now, I've got one big cloud in movement. I need somehow an emitter for the big ones and an emitter for the smaller ones. Is that the way to go?

It's a start and it ain't much, but t$$anonymous$$s is what I've got:

 public class CloudMovement : MonoBehaviour {
     
     private float speed = 2;
     private float offScreen;
     private float spawn;
     private float $$anonymous$$ghest;
     private float lowest;
     
     void Update () {
         transform.Translate(speed * Time.deltaTime, 0, 0);
     }
 }

I've searched the web, but I didn't find any solutions near to t$$anonymous$$s issue. Every answer/suggestion is appreciated :)

// erge