If you do 2 poems in depth and analyse them well and answer the question, then you should do well. If the question is at least 2, then you can stick with 2, you don't have to do 3. You cannot be penalised for doing 2. If you do 3, but the analysis is superficial then you might not get as many marks if you did 2 in depth, so it depends. But when they ask for at least 2, they imply you should do 2 or 3, but honestly, as long as your argument in sound, you have good evidence and analysis + you answer the question, you'll be fine with 2