I've put on hold debugging/testing LCDs, ADC and whatnot until I get a handle on power regulation.

Thanks to Ioannis, the datasheet for the TPS voltage regulators led me to TI's WEBBENCH; that tool is just remarkable for the newb like me. I've spent the last 2 days playing with various ICs, checking their availability on JLCPCB and such.

The 2 best features has to be that Alternate and Simulate features; you can chose equivalent parts that are no available at JLCPCB, and see exactly what the output ripple will look like.

I've narrowed down my choice to a TPS56637. I can run 5V @ 5A using 7V to 12V at 11.4mV Vout Peak-Peak; it can do more, but the output ripple degrades as you push it.

This is awesome because it gives me a wider range of power supply adapters. I was initially fixated on running on 9V to limit heat from conventional voltage regulators.

The datasheet even gives a very detailed PCB layout:

Name: TPS56637 PCB layout.png Views: 1548 Size: 80.1 KB

Thanks mucho Ioannis!