Keypads + meshing?

It’s zigbee.

You can use most mains powered devices as a repeater.

The GE zigbee light switch will work as will the Iris smart plug.

https://www.lowes.com/pd/GE-ZigBee-13-Amp-Single-Pole-3-Way-4-Way-Wireless-White-Indoor-Rocker-Light-Switch/1000097962

As far as telling what a device is, if you’re looking at the box, it should say ZHA 1.2 on the box. If you’re looking at the physical device, there should be a label with the FCC license and either a zigbee or Z wave logo. (Sometimes this is inside the battery compartment) it should also be listed in the user manual.

These are on sale right now at Lowes:

https://www.lowes.com/pd/Iris-White-Security-Alarm-Keypad-Works-with-Iris/999925326

The Lowe’s IRIS Keypad is fully ZigBee HA 1.2 certi ed and will work with other open ZigBee HA 1.2-certifed systems.