'need not be the case' vs. 'not necessarily the case': Is there any difference? If so, what is it?
Do they have the same meaning? Or do they differ in meaning? That's the main question actually.

Should I conjugate certain -ly suffixes with just one of them (sentences) or for both? I'm inclined to say: "this theoretically need not(..)" and for the other "in theory this is not necessarily(..)". Which one would you use?

Question

'need not be the case' vs. 'not necessarily the case': Is there any difference? If so, what is it?
Do they have the same meaning? Or do they differ in meaning? That's the main question actually.

Should I conjugate certain -ly suffixes with just one of them (sentences) or for both? I'm inclined to say: "this theoretically need not(..)" and for the other "in theory this is not necessarily(..)". Which one would you use?

Answer

They are all correct. Personally I would say "in theory, this is not necessarily the case."

Answer

Hot tip: "need" can work as a modal verb.

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