The 2017 Epoch Dragons set is the same as the others - a smallish base set, several variations, a couple parallels, inserts, and autographs. So here we go.
The Dragons set is the only one I know that I can't find singles in the Tokyo area. They might be somewhere, but my go-to sources didn't bust any Dragons sets. I got my singles in Nagoya over summer vacation. Packs and boxes were available (and still are as I'm writing this) but no singles. Maybe they are somewhere I haven't looked.
Variation 4 is a cropped photo variation.
I'm not aware of any five or six star variations, but they might exist. My guess for the five-star variation is an HDR version of the photo variation.
There is also a parallel of the regular cards with an "a" suffix. If I understand correctly, these have a sepia-toned background. They also appear to use the photo variation instead of the regular image.
Inserts are a little bit less complicated - only three Holografika insert sets were released: Holografika (18 cards), Holografika Rookies (6 cards), and Holografika Collage (12 cards).
It looks like 19 different autographed cards were produced as well, each obtainable by redeeming 100 points randomly found in packs.