How much could I overclock?

There is no set speed that every 2700k will get, every cpu is just a bit different and you have to go through the overclocking process to see what speed your cpu reaches and is stable at. From the people that have posted here and other places they get between 4.5ghz and 4.9ghz, a few have gone past 4.9ghz but those few have exceptional cooling and many years of overclocking experience. With just using air for cooling I would say that you could reach 4.5ghz, but you need very good thermal compound and it has to be applied right and the case will have to have very good air flow.
 
There are a lot of different makes and brands of thermal compounds and I have tried a lot of them, some normal, some high quality and some exotic but I always come back to Artic Silver 5. Your case comes with three fans which is good and the option to add more which is good also. So that combined with the Nochtua D-14 will get you to the highest that you can get on air.
 
Most likely it's ok but they never tell you what it is, however since it's an after market cooler I'm pretty sure it's good quality. The D-14 is very expensive so I can't see them putting a sub-standard thermal compound to use and they do want their product to perform well.