Tried out Castle, Tenpines, and Sanctuary. First off, they all look amazing compared to the kinda junk-y default plans :D and give them a nice new visual identity.
I'm fairly new to SS/RotC, but it was mentioned above that plots aren't generated from the plan unless they're needed by settlers, so the many rooms with no visible plot showing in workshop mode is normal? Unfortunately, this leads to some oddities such as obvious commercial plots not being there (like the Castle commissary), and there was no starting industrial plot at all in Castle/Tenpines, and in Sanctuary I had to repurpose the one plot in the middle of what looked like it should be three industrials in the generator building near the bridge to get my Logistics.
Other issues noticed in the Castle: The Martial plot on the bottom floor of the building with interior stairs should be turned 180, a poster frame thing blocks the doorway if it's set to the plot type with a desk and computer (the plot panel should be against the far wall from the doorway). There seem to be a lot of plots without power; I don't fully understand how power management in SS works but is manual connecting of wires required to get power over to pylons that isn't done by the city setup? I also have the required mod packs and still don't see the guns you mentioned for the Castle.