Thank you both, helvetica bold & HockeyoAJB. And the setup you described is exactly what I have going on, HockeyoAJB. After fiddling around for an hour or more last night I gave up. I woke up this morning and it's all working. I have to assume a full power cycle on the PS4 was what 'fixed' it as that's the only thing different this morning than last night. I should've remembered to reboot the computer...
And now that I have it working, I can even turn off CEC on the Vizio, but as noted I do need to leave it on in the receiver. And thankfully my old Logitech Harmony can handle all the input switching brilliantly.
I'm just going to post this as a mental note:
1 - PS4 to HDMI5 on Vizio (game input)
2 - Vizio HDMI1 (ARC) to HDMI out A (ARC) on receiver
3 - Receiver HDMI control on, off on Vizio
4 - TV input selected on Receiver