Hey, I just meet the same issue with the Beta OS. After consulting tp-link support, they will release new version to solve this issue at the end of this Month. Before that, we may contact App support...

you may try to add a scenes to control them with one tap.

We can only reset the plug to clear the power consumption so far. I believe TP-LINK should receive many similar feedbacks from customers. Hope they will improve this soon:-)

oh, we can't change that default SSID of plug Wi-Fi. BTY, why do you want to change that SSID?

It's recommended to take the second Deco close to the main Deco to configure. Or connect the 2nd unit to Ethernet port of main Deco via a cable and reconfigure. If still no success, you can try to...

Do you mean you can't detect the 5G signal on all your wireless clients? Have you enabled Wireless Radio? Or did you click on Hide SSID? If no, it's recommended to set the router to have a look.