My suggestion is to look at some actual floor plans for architects - they're easy to find with google, and a lot of them can be very inspiring.
Say I decided I liked the look of this house:
I could go and look at the floorplans for it, and start to convert it into a sims blueprint.
Then I could look at the floorplans:
That adds a layer of detail I don't usually think to need in Sims 4; I wouldn't normally think to build a wardrobe, because I can get all my people to change at a single dresser. Obviously, the finished product won't be exactly the same - but you can definitely get some excellent starting points just from a flooplan. Some of the best designers I've seen are very interested in architecture, so I'd use that as a reference point to start out with.