Correct.
D20 is to prevent an uncut Teensy from feeding back into the 5V rail.
H20 & D41 are to allow USB power to still power a Teensy with the cut trace.
That’s what the extra 2 pin socket is for (although only 1 pin gets soldered to the Teensy)
Correct.
That’s what the extra 2 pin socket is for (although only 1 pin gets soldered to the Teensy)