I'd call the dragonmarked houses megacorp-adjacent, but not fully megacorpy. They lack quite a few things needed to wield megacorp-level power:Eberron's dragonmarked houses aren't a bad example if you want to get megacorp-ish in your Steampunk setting. They do still have at least some government / nobility ties in most cases and mostly aren't as overtly amoral as your standard corp, but they're nevertheless up for some shady stuff under the right circumstances.
- Can't own land. Their enclaves are rented.
- Other than Deneith, can't field military forces.
- Sticks to their lane. You want to buy manufactured goods? You go to Cannith or a Cannith-approved independent. You need medical care? That's Jorasco. You need a horse? Any breeders nearby are likely Vadalis or Vadalis-approved. But Vadalis has nothing to do with hospitals, Jorasco nothing to do with manufacturing, and Cannith nothing to do with horses (though they might be able to set you up with a construct alternative). There's some wiggle room, such as both Orien and Lyrandar working in transportation, but even then there are borders (Orien does overland, Lyrandar by sea or if you're really rich by air).

