Please Help Me With Overclocking And Ram/mboard Compatibility

I am having trouble understanding all this stuff about overclocking RAM and motherboards that support it.

For my new gaming PC i can buy either:

• DIMM DDR3 2x8GB 2400MHz Kingston HyperX Savage CL11
• DIMM DDR3 2x8GB 1866MHz Kingston HyperX Savage CL9

For my new motherboard i can choose between:

• LGA1150 Z97 ASUS SABERTOOTH Z97 MARK 2
• LGA1150 Z97 ASUS Z97-PRO GAMER
• LGA1150 Z97 MAXIMUS VII RANGER
• LGA1150 Z97 ASUS Z97-AR

My CPU will be Intel i7-4790K and my PSU is a 750w Seasonic SS-750AM2, GPU is Nvidia GTX 980.

I understand that CL9 is better than CL11, but the entire overclocking thing baffles me.


What really confuses me is the following:

1. Sabertooth motherboard does not seem to support 2400MHz RAM - but it does support 1866MHz RAM without overclocking, or am i mistaken?
2. The other 3 mother boards support up to 3000+MHz RAM, but they do not support 1866MHz RAM without overclocking?
3. I do not understand how RAM overclocking works, do i sacrifice my CPU performance (or something else) when i overclock my RAM to 2400MHz?
4. If the 2400MHz RAM is left to work at only 1866 MHz, does it still have CL11 - or does the latency drop to CL9 since it runs on 1866MHz?
5. Which motherboard would be the best choice if i want to run a 1866MHz RAM at CL9?
6. Which motherboard would be the best choice if i want to run a 2400MHZ RAM at CL11?

I am not able to understand which RAM should i pair up with motherboard for maximum performance?

The prices are very similar, so money is not the problem here - i just don't understand which RAM+Motherboard would give the best performance in games like Battlefield 4 (64 multiplayer).


(side question): what is better for a single Nvidia GTX 980 GPU, a PCI (32-bit) slot or a PCI-Express 16x slot?

 

1. Processor supports up to 1600 MHz without overclocking
2. Same as 1
3. No, you just overclock memory and get more speed.
4. Depends on memory, you can try different settings, with luck they work even if not officially supported.
5. As memory controller is on CPU, only big difference is amount of tweaks MB offers.
6. Same as 5. As long as MB supports adjusting memory speeds, it's mostly about memory itself and it's ability to handle MHZ and CL settings

Buy 2400MHz memory. Motherboard does not make speed difference as long it supports 2400 MHz memory and CPU is not overclocked (better motherboard=more CPU overclock).

PCI Express x16 of course. You cannot fit that card into PCI slot.