Transferring clients to other AP's is not possible on any Wi-Fi network from any vendor. The Wi-Fi standard leaves the decision completely up to the client.
The only things you have control over is the following:
- Enable 802.11k which let's an AP provide an AP neighbor list to the client so the client only has to probe a small subnet of channels instead of a full panic scan. This feature is always on in Meraki AP's.
- Enable 802.11v which let's your AP suggest better AP neighbors to the client depending on AP load or client RSSI. This feature is also on on Meraki AP's.
- Downright kick the client off the network so the client immediatly tries to reconnect and hopefully chooses the correct AP. This is a manual action.
- AP load balancing feature. This enables AP's to not accept clients if the AP is too heavy loaded by not allowing association and not responding to probes. This feature is detrimental for fluid roaming for voice but is ok for high density Wi-Fi.