Depends on the fans and the usage. Two fans are almost always louder than one, unless you are comparing two very quiet fans, like, say, Noctua fans, to one crappy stock or low end fan that doesn't have good noise characteristics to start with. Otherwise, if you are comparing one fan versus two fans, and they are the same type of fan, two fans is always going to be louder.
The only benefit of two fans on any heatsink or radiator is the elimination of pooling or dead spots in the airflow through the heatsink or to help eliminate reversion leaks where a single push fan will sometimes lose some airflow through the heatsink by the air taking a less resistant path around the fan blades or frame, or between the fan and heatsink. A pull fan helps to ensure that all the airflow goes through the heatsink and in both cases might at best result in a 1-4°C decrease in full load temps.
If you want to make it quieter, while delivering extremely good performance, put one of these on there.
In addition to the above, a single SP fan is going to be quite a bit louder than the stock fan on the H7 (its quite a decent fan, performs well with low noise).
Two SP fans is going to be substantially louder.
Yes, going with an SP Corsair fan would be step backwards, rather than any kind of improvement. The Cryorig fan is better than the SP. The Noctua I linked to is significantly better than the Cryorig fan.