Vault 88 Defense Tips

So I am just starting my vault 88 settlement build after coming back to F4 and I mightve put on the Vault tec water pump and 200 water in purifiers before I realized defense needs to be water + food.

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So do I really need like 350 defense to keep my settlement safe?

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Is the fact that I have a supply line to other settlements also make them need more defense?

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Or is that number only really important for weak settlements and mainly focus on arming settlers and adding turrets at spawn points and call it a day?

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Thanks for your help.

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Also curious if I can even profit from 300 water for purified water farms or is there a cap?

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