You can use the Scanning API to receive connected clients along with their locations and RSSI. You also get the ssid, which you can use to filter by connected vs. probing devices.
https://documentation.meraki.com/MR/Monitoring_and_Reporting/Scanning_API
The Scanning API does not include client names (only mac addresses). If you want additional information about clients, you would use the Dashboard API (probably /devices/[serial]/clients). You would need the serial number of each access point, which you can get from the Dashboard API, from the Meraki Dashboard UI, or from the label on each access point.