Proper liquid cooling for 2-gpus 1 oc cpu?

alright so im working on a case for my current pc but when i near completion ill be going full liquid cooling, I have a asus crosshair formala z 990fx mobo which i plan on waterblocking the vcore, cpu , and 2 gpus (r9 290) the gpus are stock clocked and cpu fx8320 @4.4. im guessing 1 280 isnt enough, if it was thick would it? or what do you recommend?

The general rule of thumb is at-least 120mm per component in the loop + 120mm, so 280 is a bit too small. My guess is at the overclock you have if the ambients its exposed to are acceptable 480x120mm would do alright. Mobos don't put out much heat and even R290s can be cooled effectively with a single 120mm AIO so there is that. 

I can't really tell you what to do without knowing the case you are using. Other then that, the rule of thumb is 600x120mm of total rad for that build; though I doubt you would need quite that much. Also keep in mind as you said you can use thicker rads or ones with higher density just make sure to use good SP fans.

its going to be an open air styled case atm i have a corsiar h100i on the cpu idle is around 30-40 depending on ambient temp. gaming it doesnt get hotter then 55. gpus are running stock on 3 fans a card get around 77 gaming and 44 idle. so if i get a double thick radiator will that be the equivalent of 2x 280's or 1.5x space is going to be somewhat limited but im just trying to get an idea of what im looking for so i can build accordingly 

I have pretty much the exact same build you do. I run a 360 slim rad and a 240mm thick rad with 5 yate loons on the 360 and 2 on the 240 and I get about 55 degrees on my 8350 at 4.9ghz and 60 on my 2 r9 290s at 1050mhz. If you are overclocking then it is worth it to get an extra 120mm. Also keep in mind which fans you are use and whether or not you want to do push-pull because it does make a big difference.

Alright,  I'll run a 240 and 280 probly just normal thick maybe a thicker 240 . If I run them inline with each other or seperate them top and bottom does that make a difference?

120x120 cm radiator for each component.