All of these commands run at the router command prompt. You need to log in on SSH.
iw is perhaps closest to the hardware, or the kernel.
iw dev -- shows your wifi host devices and their names (likely wifi0 and wifi1 in your case). You will need these names for the other commands. In the rest of the examples I use "wifi0". Replace it with the actual name of your interface if necessary.
iw dev wifi0 station dump shows about all the available details about connected stations that the wifi driver is able to report. Some wifi drivers report more details than others.
Higher level commands that present the data in different ways include
iwinfo wifi0 assoclist
ubus call hostapd.wifi0 get_clients
As I said before, at the wifi level you will (at most) only have the station's MAC address to identify it. The most robust way to find the IP corresponding to a MAC is the arp table, which you can examine with
If the router assigned an IP address to the device via DHCP, the DHCP lease table will have an entry for it. This data also usually includes the hostname.
All of these commands should at least execute on a basic release install of OpenWrt.