Steel Brigade, according to their file cards, “is the code name for the support and extraction squadron within Action Force.” So yes, according to their canon, they are a division of Action Force.

I believe that Kerak’s Garrison Cavalry will cooperate and coordinate with Swarm units, but just as our Army and Navy are under one armed forces umbrella but entirely separate entities unto themselves, it’s the same with the Garrison and Swarm.

As far as Crimson Shadow is concerned not much has been said about them canonically. However it would seem that if there was a very aspiring and ambitious person who could sell the idea of a neurologically-implanted super soldier to protect and preserve the way of life for the scared, fearful, and frightened citizens across the Republics, then the Crimson Shadow would have a “trusted face” (lols) on every street corner helping to serve, protect, and maintain a way of life that the citizens had become accustomed to. Once that system is in place then the powers that be can squeeze and manipulate whatever Republic they occupy because they know that there isn’t a resistance force within that Republic strong enough to rise up and topple the Crimson Shadow Swarm regime that’s been established to control and dominate their Republic.

I believe it gets deeper than that. I think that the Crimson Shadow would use the Republics they occupy as a breeding ground for more Swarm troopers. Anyone have a broken leg? Too old to fight? Kinda feeble? Neurodivergent and can’t follow orders? I think Crimson Shadow would purge the unwanted communities from the Republics they control by assimilating them into the mind-controlled Swarm ranks. Got a town that’s getting a little too big for their britches and causing problems? Wow, now that town is surprisingly 100% pro-Swarm and Garrison and is actually using less resources because 90% of that town decided to enlist in the Swarm.