Pump speed.. 100% 24/7, variable speed, or a constant but lower speed? Googling around, there seems to be arguments for and against every side of this question, so I'm throwing it in here.
 
Situation: I will be using a Corsair Hydro X Series XD5 RGB Pump/Res on a CPU+GPU loop. That pump has the 12V power molex like all pumps, but also PWM connector to control the speed. The loop will consist of a CPU block, a GPU block, and 2 x 280mm radiators, all on soft tubing.
 
I have two port options for this on my ASUS Maximus XI Code motherboard (if it matters, either port can provide 36W, pump power draw is 30W):

• plug it into the H_AMP port (Q-fan control available so I can put the speed on a fan curve dependent on CPU temperature)
• plug it into the W_PUMP+ port (runs 100% power 24/7)

I'm reading 100% power is good because ramping speed up and down can actually cause more wear on the pump than running 100% 24/7.
I'm reading 100% 24/7 is bad because bearing wear is proportional to pump speed.
I'm reading 100% pump is good because it keeps constant flow and pressure, which leaves radiator fan speed to control level of cooling.
I'm reading 100% pump is bad because it's loud (I have not tried the pump yet so not sure on that).
I'm reading others recommend not putting it on a curve, but running it around 70-80% speed 24/7 instead of 100% in order to reduce wear, and a 70-80% speed only makes a few degrees difference in cooling so no big deal...
I'm reading it's good to use the variable to find a 'sweet spot', then set it at that speed 24/7 (but in my mind the 'sweet spot' will depend on fan speed and load, so...)
I'm reading use 100% at first to get rid of the bubbles, but then dial it back to about 70% for 24/7.
I'm reading to use the curve and keep it at maybe 60% minimum and ramp up to around 80% at 35-40C, and go 100% around 50C.
I'm reading 100% is bad because it also places stress on the loop itself and can force leaks if there's any weak points.
I'm reading that some people like to argue way too much.
 
Of course flow rate and restriction can impact this, but I'm running a fairly standard loop.
 
My preference is for decent performance cooling, but I don't want a lot of noise either since my rig sits on my desk right next to me. All the radiator fans are bequiet! 140mm high-speed PWM fans with decent static pressure.
 
Appreciate any thoughts.
 
 
 
 
 

Unlike fans, running the pump faster does not always equate to better cooling performance. Under sustained load most loops will eventually reach a water temperature equilibrium, and after that point cranking the pump faster won't do anything. 
 
I run my D5 vario at a sweet spot I found that produced the least audible noise and less vibration than higher & lower settings. Don't remember what the number was, something like 3.4. 

I usually run my D5 vario at 80% because the temps don't change between that and 100% cause, as others have said,  the water temperature reaches an equilibrium where the fan speed might help drop temps a  bit but turning the pump all they way up does not. 
 
Also, it is quieter at 80% than 100%, but honestly, I've never heard the pump at any speed except when I initially fill a loop.

Im using an EK 360mm Flat Res D5 pwm @50%. GPU/CPU loop and 2x EK 360mm PE Coolsteam Rads and have no issues. Like stated above, pump speed doesn't particularly matter once the temps equal out. What matters the most honestly is cooling square footage. I went from 1x 360 rad, built a computer desk build, and stuck in another 360 rad, cut the 6 fans down to 500 rpm and still have 5 or more degrees cooler as a whole with half the noise. Once you reach that temp equilibrium, it all falls down to surface area and max heat load, ie 1 rad vs 2+  

I have an EK pretty basic loop with a 480 rad for the thread ripper and run my pump at 100% all the time. Total overkill. It is loud as a leaf blower, but I dont mind. The thing rarely sees 50C and I have never seen 60C even after sustained hours of 100% load.