You really have more than one choice here-we'll go from cheapest to the most expensive (and has the most options)-I am using quality components in these examples, and cheaper versions may be out there, but this is what I would consider-

As far as Fan control goes:
1. This unit will turn the Fan on at 200 degrees and turns it off at 185 degrees (it also has a Fuse built-in):
https://www.ronfrancis.com/prodinfo.asp?number=AR%2D30

2. This unit will turn on/off the fan at your pre-selected Temps
https://www.ronfrancis.com/images/AR-88NEW-Md.jpg

You will need a Fuse/Circuit breaker with this:
Something like this:
https://ceautoelectricsupply.com/pro...e-fuse-holder/

Or, this:
https://ceautoelectricsupply.com/pro...cuit-breakers/

I don't the start Amperage of your Fan(s), so I picked components capable of handling up to 100 Amps-usually, a high Amp Fan will use a 70
Amp Fuse-

3. This unit uses "pulse width modulation" (basically, what new cars today use, it "chops" the voltage up instead of turning it down), so, it varies in how long it runs as well as how fast it runs (it's the best of both worlds)-

https://www.summitracing.com/parts/prf-30141

You haven't told us which Fan you are running-is it a single speed or two speed Fan?