So all of the holes on the rad/res/water blocks are 1/4"
Can I get 1/4" ID / 3/4"OD Tubing Would that mean the compression fittings to get would be 1/4" / 3/4"
There are two sides on a fitting: a thread which screws into your block/rad/res/... and a barb on which you connect your tubing.
For the thread the most common size is 1/4". Nearly all components use this size for the thread.
Now, when it comes to tubing compatibility, you shouldn't be looking at the 1/4" size of the thread, but rather at the size of the barb. In the case of compression fittings, you need to account for both the inner and outer diameter of the tubing.
To give an example: I have tubing with ID 3/8" and OD 5/8" and my radiator has screw holes with a size of 1/4". So I'd be looking for a compression fitting with on one side a thread with size 1/4" to screw into the radiator and on the other side a barb that matches the 3/8" ID and 5/8" OD dimensions of my tubes. In this case I could go for this Bitspower fitting.
So are you saying that I should go with ID 3/8" and OD 5/8? I wouldn't mind doing that and getting the right fitting for it ... I would need 12 in all I think
I'm not saying you should choose for that specific diameter of tubes. I just used it as an example.
When it comes to tubes, there are a couple of common sizes:
Size does not matter much in the case of WC, although a thicker walled tube can prevent kinking when doing tight bends. I choose for 3/8" ID and 5/8" OD because they are a bit thicker, but you can just as good pick another size. Just make sure you buy fittings that are compatible with whatever size of tubing you choose. Otherwise you won't be able to get the tube on, or worse, you can actually get leakage.
I want to go with 3/8" ID and 5/8" OD, because I think JayzTwoCents went with that one too, so why not
So what kind of tubing should I get though
Link where the tubing is: http://www.performance-pcs.com/water-tubing-soft-hard
Neoprene and Polyurethane are more exotic types of tubing, so I don't think you'll need those.
The main difference between PVC and plasticizer free tubing is, well, the plasticizer. This is a chemical that, for some brands of tubing, breaks down over time, gets into your loop and can clog up water blocks/rads. But plasticizer free tubing is slightly more expensive. You might want to do some research on the pros and cons before deciding.
For my build, I went with Primoflex Advanced LRT 3/8" ID 5/8" OD since it's cheap, has a plasticizer that does not break down, can do very tight bends without kinking and should not stain over time. Try to pick some possible brands you'd like to go with and try to find some reviews about them. This will help you decide which one will suit your needs best.