Looking at your dhcp leases should help... Most devices register a name - that should help you identify them.. If its something odd.. Looking up the mac address should tell you who made it, or atleast the nic/wifi card its using.
If wired another way to figure out what a device is, if you have smart switch that will show you the mac address table is look up the mac to what port its on, and then just trace the wire.
Many devices also list their mac on them, or can be found in info screen, etc. If trying to figure out which mac belongs to what - normally a reboot of said device will have it check its lease - so looking in your dhcp log for timestamp of what just asked as you rebooted it.
another option - if all your devices answer ping, some iot devices don't.. Is do a ping sweep for what answers, then turn off some device you don't show in your list, and do your ping sweep again - what was the IP that answered before, and now doesn't ;) What device did you turn off ;)