Is achieving the theoretical throughput of 2 Mbps possible with BLE radio with 2M PHY?

Unfortunately, no. At the time of this writing, even with 2M PHY enabled, BLE 5.x radios have a limitation of 1.2 - 1.5 Mbps due to the packet format. In order to achieve throughput of 2Mbps or higher you would have to use a different RF Technology, such as Wi-Fi.

Please see the Application Note for Throughput Testing with Bluetooth 5 LE 2M PHY Feature for the BL65x module.

(Note: The above Application Notes have not yet been added to the BL653 or BL654PA Product Pages, however, they do apply to those modules as well. The only difference is the DVK setup.)