OUTFLANK

How do units with Outflank interact with standard deployment? As one of my deployments, do I declare I am outflanking, or are they ignored entirely?

When the unit would be deployed (as part of standard deployment) usage of the Ability is declared, and the unit is then placed in Reserve instead of on the Battlefield.

How many units with Outflank can I deploy per Round?

Can a player declare and resolve Outflank before resolving the becoming of First Player from Walder’s effect at the Start of a Round?

Yes, A player may choose the order in which their effects resolve.

In Fire and Blood, can you mark units that are in Outflank?

SEE GAME MODE - FIRE AND BLOOD