After some head scratching, I deduced the following, regarding
need. I hope I have it right, like I think I do.

Please check for me:
1a) He need not work--(modal), which requires the base form of the verb along with the uninflected form of 'need'
1b) *He need work--Positive statement wouldn't be used, as it looks like 'need' is a main verb here, with the meaning of 'require.'
1c) He does not need to work--(lexical/ordinary), which requires the to-infinitive, and can have preceding auxiliaries (does).
2a)He need not be included-- (modal)
2b) He need be included--(modal), less common, as not a negative sentence
3a) He need not have worked today--(modal + perfect infinitive/perfect tense)--showing someone did something, but that was unnecessary, whereas:
3b) He didn't need to work today--(lexical/ordinary verb)--showing something was unnecessary, but whether it was done or not is not specified.
Cheers