There is no "excess" going to the TB. The regulator pressurizes the line to the TB to working pressure. The excess is routed back the the tank by the regulator. On my car this is all done right at the tank. So there is one pressure regulated line that goes up to the TB. Some explanation,
In a static case ( TB not flowing fuel but fuel pump on ). the pressure in the line is the same anywhere between the regulator and the TB regardless of restrictions in the line ( kinks, sharp bends, size changes...).
Once fuel starts to flow the restrictions matter. If there is a sudden fuel demand, the pressure will drop on the downstream side of the restriction. If it isn't too big of a flow change, the regulator and pump should be able to keep up. This is minimized when the regulator is at the TB, but then you need that return line.
There have been several ways to do a returnless system, Fuel on demand PWM control of the fuel pump. This I think has been problematic in most systems. Another is to use an accumulator to store fuel under working pressure to help accommodate sudden fuel demand, if the accumulator holds much more fuel than what is in the line to the TB, can work well. Some have combined an accumulator with a PWM pump system.
My system is more like a plain accumulator system where the fuel lines are the accumulator. I used 3/8 steel line to run from the tank to engine bay, more fuel line than my car needs. The steel line is not great as an accumulator, but I also have rubber line which is better. High pressure rubber line tank to TB would have been best. As it is, the system works. I might notice a slight lean condition initially when I stomp on it, but it is quickly resolved. I don't really know if the lean is from a pressure drop or the fuel table not being perfect. I do not see a fuel drop on my gauge where the sender is mounted directly to my TB.
Anyway, there are ways to do it without a return line from the TB to the tank.
Is that possible with the amount of fuel going into the TB, the excess needs to go somewhere.