It depends on what the opening temp the Tstat in engine is
As example if it opens at 195 F and the fan is set to come on at 185 that will cause the temps to take longer
for Tstat to open for coolant to flow, so match the fan ON setting to match Tstat opening
Better is go with a lower opening Tstat and then match fan on time for that which will bring the engine. coolant, oil and
engine bay temps down some.
If 2 fans set second one to come on like 15 deg higher then low speed (1fan)
If fan(s) has controls that allow setting when A/C comes set on so that fan(s) are fully functional
FYI
Starting with the C4 Corvettes GM added a lot of ways of controlling when fans are on or off so makes it
real easy to tune for any cooling mod changes and / or track racing cooling needs
Fan 1 On Coolant Temp. 85 Deg. C
Fan 1 On Coolant Temp - A/C On 85 Deg. C
Fan 1 Off Coolant Temp. 76.7 Deg. C
Fan 1 Keyoff On Time 1 Sec
Fan 1 Run-on Coolant Temp. 139.96 Deg. C
Fan 1 On A/C Pressure 219.9 Psi
Fan 1 Off A/C Pressure 180.1 Psi
Fan 1 Off Vehicle Speed - A/C On 35 MPH
Fan 1 On Vehicle Speed - A/C On 30 MPH
Fan 1 On Minimum Engine Run Time 1 Sec.
Minimum Fan 1 On Time 50 Sec
Minimum Fan 1 Off Time 1 Sec
Fan 1 Turn On Delay Time 1 Sec
Fan 1 Turn Off Delay Time 1 Sec
Fan 1 Off Delay After Fan 2 Off 1 Sec
Fan 2 On Coolant Temp. 91 Deg. C
Fan 2 Off Coolant Temp. 85.5 Deg. C
Fan 2 On A/C Pressure 255.1 Psi
Fan 2 Off A/C Pressure 219.9 Psi
Minimum Fan 2 On Time 26 Sec
Fan 2 On Delay Time 1 Sec
Fan 2 Turn On Delay Time 0.4 Sec
Fan 2 Turn Off Delay Time 0.6 Sec
Fans Off Vehicle Speed - A/C On 90 MPH
Fan Type (0=2 Fans, 1=Aux Fan, 2= None) 0