Say that the Imperium discover the world of Warhammer Fantasy and ask the Empire of Man to join the Imperium, which they do. Then the Empire made regiments for the Astra Militarium, what would they be like? Not just by looks, but also by tactics, culture, and behavior.

I imagine that a Guard Regiment from the Empire of Man would be heavily artillery based. Actually somewhat similar tactically wise to the Semtexian Bombardiers, actually: Dug in infantry protecting and acting as a wall for the enemy to slam into while the Artillery chews the enemy to pieces.

7495171
Yeah, to me I think they might do something like the pikes and shot. I heard that the armies of the Empire are known for looting, though I could be wrong.

7495813
I think that's Norsca and Estelia. Could be wrong though.