You should have your fans set to shut off at least a few degrees above your rated thermostat temp. Otherwise they may turn on and not shut off until you are done driving the car. When I had a set of electric fans I found that most switches usually had a roughly 15 deg spread between cycling on off. I had mine set to cycle on at 205 deg and back off at 190 and had a 180 deg thermostat.
Don't listen to everything you hear about aftermarket electric fans not cooling very well. They do work, you just need the right size fan(s) and expect to see your engine temps cycle up and down as the fans turn on and off while you are at low speeds.
I had dual 12" fans in a mild supercharged 350 in a 72 K5 Blazer.