Have you done a Compare on EVGA's Website, it works really well. Based on Card Models
"break down the improvements" this can take a lot and lots of Posts.
FTW First Generation FTW2 Second Generation New FTW3 is now out. Model Types  and ACX & iCX are Cooler Types.
Evga 1080 FTW vs FTW 2 - Overclock.net
A new GTX1080 FTW from EVGA! What is the ICX FTW2? - YouTube
What the HECK is EVGA "iCX"? GTX 1080 FTW...2! [No longer private ...
What are the differences between all those different GTX 1080's ...
 

EVGATech_BrandonS
I would recommend THIS ARTICLE; it shows the iCX improvements. Performance and temperatures remain about the same, although I've seen a couple people say their GPU temps are a little higher since more heat is being transferred to the cooler. The specs between the cards should be the same otherwise. 

Why is it so hard to find that Page and really any other Tech Items you use.
I was so easy last year compared to this year. Maybe a Tech Page Listing your Cooling Changes over the years.

Yes, I spent an hour looking and gave up. But you posted what was needed so all is good. Thanks

EVGATech_BrandonS
I would recommend THIS ARTICLE; it shows the iCX improvements. Performance and temperatures remain about the same, although I've seen a couple people say their GPU temps are a little higher since more heat is being transferred to the cooler. The specs between the cards should be the same otherwise. 

Actually, this is a more recent article:
https://www.evga.com/articles/01104/evga-geforce-gtx-1080-ftw2-sc2-11gbps/
 
10% more memory bandwidth on the FTW2 and SC2 due to the 11GHz memory. Since it's through a firmware update, it was not marketed like that at the start and all the reviewers only reviewed them with the 10GHz setting.
 
Unfortunately it was not offered to any ACX users:
https://forums.evga.com/EVGA-GeForce-GTX-1080-FTW2-and-SC2-OPTIONAL-11GHz-BIOS-Update-Available-Now-m2652350.aspx
 
At first I was kind of wanting to get the FTW2 over my FTW and I had considered taking advantage of their upgrade program, but decided to opt out when I learned that the sensors were proprietary and the only way to view those temps is to use the EVGA Precision software.