Hi everyone.

I'm pretty new to the game and want to try out the bombers and fighters module. I heard that the best bombers/fighters are only available via a quest called the living plague, is this true? 

If this is true, do the quest require any prerequisite to trigger or is it pure RNG?

You've heard wrong. Heavy Fighter and Light Bomber (require Adamantian), Strike Plasma Bombers and Strike P-Laser Fighters (require Antimatter) are possible rewards for successful completion of "A Swarm of Locusts" cooperative quest. Quest has a 25% chance to start every turn once game reaches 60 turns on normal speed and after you unlock Stage 4 of Military quadrant of tech tree.