Dave C, I do not have long runs back & forth. Power goes from TIU directly to control panel, and then out to blocks. I agree completely with your choice of wire gauge. When I built 8x4 layouts with centralized control panels for young grandkids, I used 16 gauge. For anything larger, 14 gauge with a 12 gauge common buss.
When I built my layout about 1992, relays were expensive. The cheap Chinese relays hadn't arrived. But when I rebuilt my postwar Lionel gantry crane to move, I used relays and cheap power supplies for those relays, so I have 22 gauge wire running from panel to crane.
Electrically, I can see no difference between running power to the center of a layout and then running feeds from there to blocks, or running it to a control panel and running feeds from there to blocks.