Imperial Dwarfs are all of those Dwarfs that have left behind their Karak-kin believing that the defence of the last Dwarfholds is a lost cause and thus they choose to start a new life with the Manlings of the Empire.
This Is not surprising if we consider that the Dwarf kind feels an enduring debt to Sigmar and his heirs since the battle of Black Fire Pass.
While this choice has caused some "problematic relations™" with the Karak Dwarfs, the Imperial Dwarfs successfully managed to preserve their original culture,religion and language and also managed to integrate with the imperial society.
As a matter of fact, Imperial Dwarfs are considered the “second people” of the Empire, its most important race outside of Humanity itself.
Since We are mainly interested in the military portion: Imperial Dwarfs have served in provincial and Imperial armies for over four millennia and even helped Magnus The Pious against the hordes of Chaos.
They are known as steadfast troops who are proficient in the use of spears, pikes, and handguns.
*Considering that all of this data Is from Warhammer Fantasy RPG 2nd and 4th editions, is entirely up to you to decide if this mod Is Lore-friendly or not.*