On the GZ the differences are:
2K2 have clamping low rise
Clamshell grip
metal eye covers
new fade colours
On the "stock" 2K2 Timmy
You get metal eye covers
Dragon Trigger
They now come with semi-only board rather than the old select fire.
If you have a choice, I'd def go for the 2K2 versions of the stock or GZ.