Environmental impact assessment methods

A national government hesitates between setting up, on a large scale, support policies at the national level (via instruments such as subsidies, bonuses, tax advantages, etc.) for the installation of photovoltaic panels or the purchase of electric vehicles (both for individuals and businesses). They are aware that such policies can have both direct and indirect impacts on the economy, sectors and the environment. The government wants to stimulate the technology that will lead to the greatest reduction in the environmental impact of its country / economy.
What environmental impact assessment methods do you propose to inform the government on this subject? Give:
a) The method(s) that you would advise to perform and, if several, the sequence / order in which the methods should be applied,
b) Argumentation why the advised method(s) is/are suitable for the given situation, and
c) The main shortcomings / limitations of the method(s) you propose