I never use them but wouldn’t say I’m a pro either. And I think blueprints are a good idea, and probably very useful for those who want a faster creation process so they can get to playing sooner.
But I love to build and decorate and enjoy spending my time playing with colors, patterns and textures. I build my structure first, and only fill/decorate the interiors once I’ve completed an exterior design I like. I think I would have a difficult time with trying to puzzle/piece various preset rooms together and still create a structure I’d be happy with. And the fun I have building and experimenting with various architectural styles in game is equal to my enjoyment playing in live mode.