I did edexcel aswell.
Yes I suppose you don't really need to use case studies for that specific question and you should use evaluate the strengths and weaknesses between each measure.
Oh, if you didn't find a mark scheme for that specific question, you could just search any random past paper 20 mark evaluate question and look at the mark scheme on how they award marks to students so that it gives you an idea on what points a 20 marker should include. Plus, looking at sample questions/examiner feedback (i'm not sure if its only available to the sixth form/college or online for everyone) is quite helpful.
PEELCEEL is Point, Evidence, Explain, Link (to the question and point you made) 2nd paragraph Compare/contrast?, Example, Explain, Link (to the question and point you made)