But i think it's better to drive flat out in SCTEX...it's got wider and smoother roads... 
The main advantage of SCTEX is the straightness and properly banked highway. Also having much less traffic helps maintaining a high speed of travel along this highway.
The 100kph speedlimit on this road is really too low. Makes people sleepy and that could be more of a hazzard to everyone else.
Are there any people or cameras that will catch you if you're speeding in SCTEX?
There is the highway patrol but you can see them if they are on duty. Just look for the white unmarked Toyota Hilux parked on the side of the highway or on top of a crossing bridge over the SCTEX. If you spot one parked without any other vehicle near it, chances are its on "speeder" duty. If you see one with another vehicle, it would be assisting that vehicle. Best to slow down to below 150kph to avoid being too obvious about your speed.
The usual tactics in avoiding getting caught is simply slow down to legal speeds before reaching a blind rise or curve in the highway. When you reach the rise/curve, take a good look into the distance for that HILUX parked somewhere. If none are seen, accelerate to your preferred speed.
So far no automated cameras installed on the SCTEX.