solid setup man might want to get water cooling if you plan to overclock and can afford it.
1. Tons of water coolers will work, H100i is the best
2. A HDD will give you more memory storage for a cheaper price but an SSD will have less memory and be more expensive, but it will be faster than a HDD
3. A 960 might not even play a 4K game, might want to get a 970 or 980 if you want to play in 4K with a playable fps (get a 970 just to be safe if your not gaming)
4. You can either check on the manufacturer's website or look at its specs on the website you bought it on