[help] Arduino Controlled voltage from Switch regulator

Hi. I'm quite a novice with electronics. But I am working on a Arduino based fan controller.

I'm going to have 4 separate voltage delivery outputs. for each of the fan groups.
Each group will be loaded different.
The output with the most load will have 4 fans connected. Each fan is rated ca 200mA.

I'm using the pc's own power supply to power this.

I wanted to adjust the the voltage delivery to the fans. (thus adjust the speed)

I'm considering to use switch regulation to provide voltage to the fans.

I wonder how to build this circuit. I would be glad if someone could help me design.

I suppose each set's speed will be determined by the temperature?

So you will have 4 temperature sensors?

Now sure why you are making it more complex by using a micro-controller. 4 circuits will do the job and have the virtue of being independent [if the arduino circuit fails for some reason you lost control for all sets]

Using switch regulation makes it more complicated and can induce noise.

What voltage range do you want? Making it a simple off/half-on/full-on would be simpler and probably just as effective.

The Fan speeds are going to be mostly adjusted by manual buttons ( I guess I could use a Potentiometer, but I'm using simple press buttons for the looks)
The only group of fans that would be controlled by Temp. Is the group attached to my radiator. In this case it's going to be controlled by temperature data provided by pc.

The reason I'm using a micro-controller is because I'm planning to have rmp displays, USB Feedback and The option to control this device though software on my pc.

The Voltage range I want this on this controller is 6-12V.

I know switch regulation could make a lot of noise. But in worst case I guess I could do some extra shielding an filtering to prevent too much noise coming into the system.

I could always consider using linear regulation. But since at lowest speeds the transistor would have to break down 6V x 0.8A. It would end in the transistor causing 4w of heat. Such an amount of heat would not be a thing I want.

I know this might be a bit advanced for a person who haven't worked too much with electronics. But it's supposed to be a home project in addition to school. (which is in fact Computer and Electronics )