As I understand, the newest Blackberries on US TMO and some Canadian carriers offer a software-based WiFi Calling that differs from the older UMA-based wifi calling approach.

How does this differ, beyond the inability to switch from WiFi Calling to cellular coverage during a call?

What does this mean for router setup? And new tricks on the router and/or WiFi configuration?

No difference in setup. Doesn't work any worse or better.
The new WiFi calling, as you noted, dies when you leave the WiFi area.

Just to be sure, a now disappeared official Blackberry tech article said TCP/IP Ports 443, 500, 4101, and 4500 to cover UMA, BIS, and BES.

Any other ports that should be open? Any need to differentiate TCP vs UDP ports?