How can I blueprint a boardgame's mechanics?

Basically - yes.
The circumstance deck introduces additional, well circumstances. It can mean that a wild animal enters the combat map for no reason doing something. The animal itself is drawn from the “Animal” deck, which also has its parameters (i.e. different animals can be found in different terrain with different frequency, so it to would have “compatible terrain” icons clearly seen when faced down).
This is only one of dozens of possibilities.
It could be that a hostile group, defined on the “Encounter” card, say - a raider group has some quality. It could be their change of stats (i.e. they have better armor, or automatic weapons), greater numbers, higher morale or a powerful NPC on their side (again - drawn from the “NPC” card deck, but only from those NPC cards that have a ‘bandit’ icon clearly seen while faced down because not all NPCs are combat-ready and prone to banditry).

So, as you can see - the amount of cards to be resolved is pretty unpredictable and largely inconsistent, because an “Encounter” card can mean no additional cards to be drawn.
The idea is to primarily build a platform to observe this dynamics, so that scenarios can be simulated.
Ideally, it would be via filtering. So that I could design and introduce all the graphics, the tokens and the miniatures of the board game to the Unreal Engine, so that, for instance, I can set parameters so that possibilities and probabilities can be observed.
For instance, let’s assume that all decks, tokens and the map are all in the engine, in a 3D environment emulating something like “Hearthstone”.
I take the turn counter so that it dictates the weather and the day-night cycle, which has an impact on some cards.
I take a character and place it on a map area.
This narrows down the Encounters that the character can encounter based on said parameters, the NPC that can be encountered, etc.
Ideally, such probing would prompt the display of plausible and playable scenarios so that probability can be observed.