Howdy, fellas!
Eric, I knew you'd figger it all out!
There is no Tamiya PE screen set available for the Tiger II, but they do make a set for the Tiger I. 800 yen here in Japan.
I haven't seen those brass barrels, but there were two types used on Tiger IIs: a one-piece deal and a two-piece deal. The older Tamiya kits did not come with the nice aluminum barrel the new release has, so those barrels must be aimed at those kits. Also, the Porsche KT comes with the 2-piece barrel, while most of the actual vehicles were fitted with the 1-piece barrel.
I think the aluminum barrel included with the new kit is great. The muzzlebrake is still a two-piece plastic affair, but I reckon it's fine, too.
Tamiya also included a PE Zimmerit set with the newest RC KT. I don't like the looks of it, but they may release it separately in the future.