To shorten the description a bit and have a better list of issues / quirks of the mod I've decided to create this discussion.

The blueprint object itself is only 1 tile in size and it is positioned where the cursor is, it doesn't require an anchor point but the space does have to be clear in the foreground.

Pink tiles shown on the hologram will take on the existing tiles in the world, if pink tiles are within a building it means the building will pick variations of rooms to add a bit of randomness.

Sv tiles take on the biome primary dirt.

If the building is showing no floor then make sure you place it on a flat surface otherwise the objects won't spawn.(Tiles will though)

Floran hut buildings are supposed to be in hills/mountains, placing them outside of these will result in missing tiles.

Sometimes a piece of the building might be missing when intersecting with other dungeons, this only seems to apply with large buildings.

Some objects will likely be missing, this seems to primarily affect larger buildings. Obviously if you place a building in the ground then outside objects will be missing because tiles will be in the way.

The generator in the ocean city doesn't work, i don't know why.

Lastly don't use a blueprint on your ship or next to protected tiles because it will destroy it. (This shouldn't matter if you use build your own ship mods.)