Contract drops are random!
They are rolled with a rarity system, with Common, Rare, Epic and Legendary cards, and the possibility to have Elite versions too of these drops (2% chances).
Every contract has its loot table though; finding Epics for instance is usually easier than on Boosters.
The final drop tables will be shared on wiki before contract opening. Note that only Syndicate has a legendary at the moment, and that drop tables may be refined over time to keep value in the contracts.
Thanks for an in depth answer! I also found the simple answer to my question in your post afterwards (sorry for missing it in the first place 😅) - but this elaborate answer was even better!
Happy development 😉