I have really tried searching but i'm not having the best of luck in finding a definitive answer on this one. (i have the X58 e767 SLI3 board, fyi)
 
Is there a maximum size per ram stick/per module limit on ram size with the W3680/90's? Like 4gb per stick? 
 
I have read that there is a max of like 24gb on the chip via intel's website, but i don't know if that means the sticks of ram, each, cant be over a certain size. Do they mean 6x4gb=24gb???
 
And then there are a ton of threads out there that have people who have used more than 24gb on Xeon processors, but then the threads get saturated with people running a X56xx chip, which allows for wayyy more ram than the W36xx. And i cant find a definitive answer specifically on the W3680/90 chip, but TONS of ram info on the X56xx chip. I also have found info of people using more than 24gb, but have done so with more than 3 dimms, like 6gb per dimm.
I have also read plenty on people being able to go faster than the chips limit of 800/1066/1333, but again i cant find how many GB per stick people have been able to go to on the W3680/90. 
BUT i want to make sure they don't mean 4gb per stick, as is 6x4gb = 24gb max, when is refers to 24gb max for that chip. 
 
I want to install 3x8gb of dd3 1600, which is under the posted limit of 24gb. I do Not want to have to go with 6x4gb, i want to go with 3x8gb. 3 dimms are easier than 6 dimms when it comes to overclocking, and the memory controller, and getting ram stable and so on. 
 
Where are my W3670/80/90 people at? 

on my w3680 I have 36gb of ram and works fine. The ram limit that is stated is the ram limit of the time because that was the most dense sticks at the time. I have tried 48gb in a evga x58 classified and it works just know if you plan overclocking that is when you might run into issue but it is usable up to that amount as far as my testing went.

This also boils down to the stability of the memory controller in the CPU and the memory used. On that system (X58) I would never attempt anything above 24GB myself but some people have achieved higher memory amounts. 

I wanted to share my results, as i couldn't find much for this information when i was initially searching. 
 
I was able to install a W3690, OC'd to 4.2ghz (33x133) and 24gb of Corsair 1600mhz ram without issue. I used 3, 8gb dimms, installed in the slots that my boards manual states they should be installed when using triple channel and 3 dimms. (cant find crap for triple channel kits anymore, so i bought a 4 channel 4x8 32gb kit, and just have a spare 8gb dimm)
 
I did find out that no matter what settings you use, 2:10 or 2:12 or so on, you cannot have this ram at more than 1333mhz. The only way this ram will go over 1333mhz is with increasing the BCLK to above 133. I have to assume this is a CPU restriction with the W3690, as i have 2000mhz ram installed on this same system with my old I7 920, and reached 2000mhz, without having to bump the BCLK to do it. 
 
I personally went with a W3690 to get an unlocked multiplier for ease of overclocking. I'm good with 1333, and i don't think most people would notice the real world performance between 1333 and 1600 speeds. IMO FWIW
 
Anywho, that's my results.