Source: Anandtech (IGP is the turbo boost of the integrated graphics and, on the Cores row, “T” stands for Threads.

Additionally useful information:
* All use Intel’s UHD 630 integrated graphics
* All support HDMI 2.0 and Display Port 1.2. 
* They must be paired with DDR4 RAM (not DDR3 or DDR5)
* All require 300-series motherboards (100 or 200 series won’t work).
* The “K” processors can be overclocked but you will need to buy a separate cooler
* The non-K processors come with a cooler but cannot be overclocked. 

Is it worth upgrading to a Coffee Lake CPU?

At the moment, the motherboards for 8th gen Coffee Lake CPU’s are very expensive (in the $110-160+ range easily).  That’s almost twice as much as 7th gen Kaby Lake motherboards.  When the selection widens and price goes down, Coffee Lake is strongly recommended.  However, price is an important factor.  While Intel’s 8th gen CPU’s may very well be 15% better than their 7th gen as claimed, the extra $50 added to your overall bill cancels that out.  However, high-end users, hardcore enthusiasts and professional content creators may find the investment worth it.  

Of course, the i7-8700k is king of the hill right now, but even the i5-8400 and i5-8700k are edging out the Ryzen 7 1700 in benchmarks.  Most remarkably about Coffee Lake is just how far i3’s have come.  With 4 cores, at 3.6-4.0 GHz clock speeds, the i3’s have shown respectable benchmarks and are similar to where the i5’s and i7’s just a few years ago.