Question Ridiculous temperature spikes

[Semp]

Just built a new rig:
i9-9900k
H150i Pro corsair cooler - 360mm, 3 fans.
ASROCK Phantom Gaming 9 Motherboard.

Something is very wrong with my rig, and I've got a few ideas but I want to know if this is immediately diagnosable by ear:

Idle, sits at 30-35 degrees C.
Using corsair link, I can see the pump speed doesn't change relative to the temperature of the cores, was sitting at 2300, I've put it on "Extreme", and it now sits at 2700.

If i open blender and do any kind of intensive 3D render, the temperature of the cores goes from 30 to 95 degrees IMMEDIATELY, up to 105 degrees. As soon as the render stops, it drops back to 30 in under half a second.
HWMontior agrees with these temps, and so does my experience as the screen tended to freeze slightly.
When gaming (BF1, max settings), it doesnt seem to go over 60 degrees, when under about 40% util, gettings 110ish fps at 1080p.
The AIO coolant temperature never gets above 35 degrees.

Now to diagnose how I've been dumb:

Extra info:
Ive got the cooler plugged into "CPU_FAN2/WP" as the WP seems to stand for water pump, and "CPU_FAN1" doesnt have that postfix - is this something I should change?

Cables are all properly plugged in, USB to mobo, the 3 fans to the 3 connectors running off the cooler.
Radiator is front mounted and the 3 fans on it are on intake, and all running at 1300 -1500rpm.

H150i Pro came with pre-applied thermal paste. Reseated the CPU once already whilst diagnosing another problem, didn't clean or apply new paste as it didn't seem necessary, paste on there was still fine.

So, to all of you experienced fellows, is this a problem with my pump, my configuration, thermal paste, or something else?

Cheers in advance

 

[Semp]

Just removed the default thermal paste from the CPU and reseated with some Arctic Silver 5, exact same temps and problem :/

Anyone got an ideas?

 

[Semp]

Ok so from using task manager I could see that despite being a 3.6ghz i9-9900k, when I was doing these actions in blender it was reading 5GHz+, so I wondered if this could be a turbo problem.
Found that you can basically turn off turbo by going into power plan and setting it from 100% to 99%:
Method to turn of turbo as suggested by this guy in this artcle.
Task manager now reads as 3.6Ghz, and nothing is making my PC go over 55 degrees now.

The better question now would be: How do I allow turbo, but limit it so it doesn't literally cook my PC any time I hit 100%?