There is very little fluff on the actual look of cogforts. These stories contain pretty much all we know.
https://malignportents.com/story/iron-and-oak/
https://malignportents.com/story/the-offer/
The first story gives an initial idea. Says, On her piston-driven legs, she carried us ever eastwards from the city walls, and the light of civilisation dawned anew in her wake. Chaos warbands broke like waves upon her ironclad flanks. The Story then describes some kind of network of cogforts creating a shield web around Hammerhal Aqsha. Also mentions a draw bridge.
The Second story gives more details. Such as the cogfort having 17 gun emplacements (cannons, organ guns, and a large center piece cannon.) Alarielle then splashes the cogfort with a wave of swamp water which is "several dozen feet high" which almost goes over the cogfort wall. So about 60-80ft tall at the cogfort' deck.
The first story is in Aqshy, the second is in Ghyran
I heard there is a bit more fluff in the Soul Wars novel. This is all I have so far.