Models

Yes. In fact if the examiner says 'using a model or models of your choice' you would be foolish not to use more than one. A model rarely gives 'the truth' on its own. So PESTEL tells you somehting about the macro-environment but to make sense of the competitive environment, 5 Forces is needed. In some questions you might also use something like product life cycles to talk about products in their decline phase which need urgent replace emtn to keep the company revenue up.