Depends on your temps. If you have a hot system in a hot room, you may need more fan. Or not.
Look at it this way: you need a dual fan system. One part could be just a simple vertical rotating fan sufficient to blow the plants around gently. That to strengthen the stalks.
The other is to control heat and humidity in your tent, and that consists of at least the Cloudline. For my own 4x4, with 600W LED light, I had a small clip light at the top blowing across the light ballast. Because I'm tight on space up there. I also have the Cloudline up there with a big muffler directly over the top of the light. That was doing fine until my plants filled the tent. Rather than defoliate a lot, I put in an input fan, 6-inch, running 24x7. The Cloudline is usually running at low speed or off at night. Both together keep temp down (79F) and RH where I want it (50-53%). The input fan also balloons the tent from the overpressure, and that gives my buds a little more space.
