I just had to put the components in the case and plug the cables. One of the kits just needed the sensors to be attached to the female pins already soldered in the board. It took me less than 10 min to assemble both.
The kids doesn't mention any wifi/zigbee/z-wave capabilities, which would mean it would need to be connected to your HA unit with a cord of some sort (it references a USB cable on the page). That's a hardwire connection (as opposed to a wireless connection).
Got it. They have an ESP chip in them, so they have wifi.
One is ESP32-C3 and the other is ESP8266.
But I'm powering them with the included cable, which is pretty decent. You can certainly power it with battery but I have no idea about its power consumption.