The only two benefits of NCS is a four eye check and that you get to keep your passport. a bit steep at 50 quid for that tho.

Do certain type of applications take longer than the others?

TBH, HO don't specify exactly what is required, same with accountants. I thnk its left at the discretion of the applicant and caseworker alike. You have to pay attention to some categories that have clarifications specified in paranthesis. for eg. Civil servant (permanent), Valuers and auctioneers (...