I don't know, but I always thought the Enclave we see in the CW came from the Oil Rig and Navarro, with nothing coming from Chicago. Even then, I don't see why all power armor from that region has to have this specific look to it. I would think the Enclave in Chicago would still use the power armor used exclusively by their faction.

Anyway, I would think the power armor they would arrive in the CW with would be the same advanced power armor Mk I and Mk II we saw in Fallout 2, but apparently its this "Enclave power armor" we see in Fallout 3, which is referred to as the Mk II version of the advanced power armor despite the Mk II looking exactly like the Mk I. It just adds a lot of confusion to lore that inconsistent enough as it is. So I would find it more simple if this X-01 we see in Fallout 4 is the armor the Enclave have always worn (which seems to be the case if it's appearing on the east coast for some reason), while the design we see in Fallout 3 is retconned and redone if Bethesda decides to have the Midwestern Brotherhood appear in the future.

they had been in dc for a while if I recall. Autums father was the one who led them there after getting a message from eden. They had just been laying low for a while. As for the armor it has some inconsistencies in fallout 2 and 3. In 2 it was suppose to be a new light weight but stronger armor but it ended up heavier and not showing no change in appearance. It also didn't have much of an appearance of being light weight. The new design could have been beth trying to change that, or it could've been beth showing progression it's hard to say. Fallout 3 has alot of lore errors, though I suppose that can be expected since it was their first venture into the franchise.

An unused model number from the concept art gives the Fallout 3 Enclave armor as model A.

It looking different can simply be explained by it being a different model.

No, I'm pretty sure Power Armor IS Power Armor. In Fallout 3 and Fallout New Vegas, I'm pretty sure they just didn't have the time or capability to make Power Armor a sort of vehicle with the core you have to put inside.

But the military and government didn't take full control of FEV. It was still West Tek scientists. When the government wants to control something, they kick out non government scientists and bring in their own team. The government was just providing security and location for the project to continue, and supervise. They called the shots, but it wasn't a total government takeover.