I’m not sure if turbo airflow scales linearly with compressor/turbine size in real life.
What I’m saying is in the third image I adjusted the twin turbos to the right size so that they made 241hp using 8.88psi boost at a similar rpm.
Given an equal level of airflow (as the engines have identical head flow characteristics and boost pressure), two twins should have less lag and more responsiveness compared to a single turbo, though I’m not sure if two twins together flowing the same amount of air a single will have a lower boost threshold compared to the single.
My point is given a equal level of mass airflow for each system, twins seem to have equal responsiveness and a higher boost threshold where they should have higher responsiveness and an equal boost threshold.