Hi Spyder,Normally if there's plenty of space, they'll put it in the top by default.
It's only when there are restriction in the case not supporting the size of the radiator in the top (doesn't apply to this as can support up to 420mm on the top), or if there are other restrictions such as RGB RAM can cause a clearance issue with the radiator in the roof as the RAM itself is quite a bit wider and so hits the radiator. This again is not an issue with your build as you don't have the vengeance pro RAM which is the RGB stuff.
This is a really roomy case, so great for these threadripper builds that require more breathing room.
Thanks for all your help on this. One final question on the Fractal Meshify S2 case. Can you adjust the speed on the pre-installed fans?