BEM theory would help you to assess the performance of your rotor model in terms of power and loads encountered at different elements. Integrating the same, you would be able to determine the overall performance of the model. The BEM calculation will slightly over-predict the power output (as compared to the data used for validating) as it doesn't account for wake losses.

For identifying the wake structure, CFD implementation would be a good idea wherein you would be able to model the wake region and validate the same with the BEM code. How do you find velocity deficit using BEM?

there are some kind of Wake Geometry Model which u can use to predict the wake structure...

u can find these models in the following book, chapter 6.

David A. Spera, "Wind Turbine Technology, Fundamental Concepts of Wind Turbine Engineering".

The BEM method does not account for turbulent effects in the wake, so it cannot properly predict the wake development. It is very good, however, to describe the local operation of the turbine.

BEM does not account for turbulent effects in the wake.

However if BEM is coupled to CFD model, you can identify both near and far wake of the wind turbine

There are a few empirical models that can predict (quite accurately) the overall velocity deficity and turbulence intensity in the wake of a turbine. However, these models do not predict the near-wake as accurately as one would hope. This, as far as I think, is because of the helical vortices created by the turbine. Please note the following as references

1) For velocity profile in the wake: Jensen NO. A note on wind generator interaction. 1983

2) For turbulence intensity decay in the wake: Hansen MOL. Aerodynamics of wind turbines (Chapter 2 I think) ..

However,  I would like to add that one primary parameter that is usually ignored and is the main cause of unsteady loading on downstream wind turbines is the rate of change of wind direction (can be up to and even exceed 30 deg/s) .. However the mean wind direction remains primarily unaltered even after passing through the blades..