The first edition with 84 units, 12 rewards and 12 feats.
Are there any rule changes in later editions?
Do the extra units added later balance the game more?
The latest rules can be found in the Files section, titled "Omen: ROW RULES (official Omega Edition 2014 Rules)"
I've only ever played the latest edition so wouldn't be able to make any comparisons to previous editions.
Definitely a fun, balanced game