If you have time, use it to dig in the forums to gain knowledge.

software : speedfan for example

There is temperature inertia in a waterloop, cpu and gpu have thermal protection.
If your are that worried, use two pumps in series

1/2 internal diameter is overkill
3/4 is good and a lot easier to use

The ps06 case is too small for watercooling .

It will be difficult to have recommandation if your don't specify the context :
- budget
- maximum size of case
- level of noise desired

if it were me for a cpu+gpu with a little overclocking, in a very quiet setup i would use :
- 4 x 120 elements or more, alphacool for example
- a d5 pump or mcp35x, you can set those pump speed and noise
- quiet fans like : noiseblocker m-12s2 or be quiet silent wing 2 with a fan controller