The PHY rate is dependent on the MCS chosen. The MCS is chosen is based on the SNR at the receiver. And the SNR at the receiver is dependent on the transmit power and the propagation losses in the channel.

It would be difficult to combine all these effects into a single formula, which is why I would think a simulator is required.

This is explained in some detailed in the 5G NR Physical Layer white paper in https://tetcos.com/5G-white-papers.html

Sai R N and Ananya Hegde. Thank you for the answers. I tried some examples.

SNR is not an "input" variable in NetSim. Hence, I need to change some other "input" variable which would affect the SNR.

Am I right in assuming that the SNR changes depending on the gNB-UE distance, the gNB transmit power and the pathloss model used?

Harshitha .. Yes you are right. SNR depends on these plus factors like the band used (FR1 or FR2), number of transmit and receive antennas, how is power allocated between the antennas, beamforming, mobility (distance will then change), etc.

Sai R N Would it be possible to provide details of how the MCS is chosen per the SNR? Is this also known as Link adaptation?

You can see these discussions

See https://support.tetcos.com/support/solutions/articles/14000136717-calculating-the-5g-data-phy-rate

The link (https://support.tetcos.com/support/solutions/articles/14000136717-calculating-the-5g-data-phy-rate) explains how NetSim calculates the data rate using the 3GPP standards formula that considers factors such as bandwidth (BW), modulation order (Q), code rate (R), number of MIMO layers (N), and overhead (OH).

My question is: how can I calculate the avg. data rate when the UE moves? How can I validate the results got from NetSim against the 3GPP standard formula for the case when the UE is moving?

The correct way would be to take the time average. You would need to take the Modulation and Coding Scheme (MCS) values at various time intervals, compute their mean, and then incorporating this average MCS into the 3GPP data rate equation. This average MCS will give you the modulation order (Q) and the code rate (R). All the other variables in the equation do not change with time.