@DarkMatterMatt On the subject of wiring, it is worth spending a long time to get everything wired safely and securely. Replacing that one extension that runs all the way down your lift is awful, so make absolutely sure that it can't be caught on gears or in moving parts. Leave spare wire around hinge points so that the wire doesn't get stretched when the joints hinge. Would also recommend putting 6 motors on a power expander (use two Y-cables).
I fully understand that either of us may be wrong on which is and isn't correct. But on the last statement, generally speaking, it is better to stay with having only 4 motors on the expander and not 6 for PTC distribution reasons. The expander has one PTC for all 4 ports, and the CORTEX has 2 PTC's, one from ports 1-5 and another from 6-10. It would help prevent problems if you distribute evenly across all of the PTC's regardless if the CORTEX would consume battery more. So generally speaking, I would suggest 4 motors on 1-5 PTC, 4 motors on 6-10 PTC, and 4 on the expander to ensure that you're getting as even of a distribution as possible. To improve consistency, I would also suggest having the drivetrain be distributed between the 1-5 PTC and 6-10 PTC and never on the expander since the drivetrain is the most important subsystem of a robot.
The ports 1 and 10 topic I generally don't want to give a solid answer but give an answer that I follow myself from personal experiences, regardless if wrong or not by the general public.