You are quite right..only the middle one ( twin fan outboard engined ) has been developed further...and indeed there is a change made to lift the engines higher to cleaner air further from the vertical ( albeit not sure how far it ought to be from it ). My last design was a tractor model in classical style ( very conservative ).Topspeed, your enthusiasm in designing aircraft would be more fruitful if you would consider some basics of aircraft design. If you would read the books The Design of the Airplane and then Anatomy of the Airplane by Darrol Stinton probably most of your questions would be answered. He was a great mind and his books are excellent for understanding the basics of airplane design and why some planes are built the way they are. He left the World early this year but his books are a legacy for humankind when it comes to understanding the aircraft flying principles.
All three of your designs posted here would not be able to fly at all. If you read these books you could understand why your first design would be fatal because of design induced oscillations, the second because of the propwash too close to the ground and vertical stabilizer, etc. The third design has also so many issues most probably from trying to use the principles of jet fighters in small homebuilt aircraft. While fighters have to be unstable to have better maneouvering abilities it could be lethal to such a small aircraft. After reading the books you will have a clearer picture why some small details are quite important for successful flight.
I am impressed by your expertize and keen observation...reading is always good thanks for the advice.