The urgency plus the Mac plus no Notes install narrows this to one clean strategy, converting NSF to the MBOX format Apple Mail imports natively, since Apple Mail speaks MBOX and NSF converters can target it. The path:

The format target that makes this work: Apple Mail imports MBOX directly, File, Import Mailboxes, Files in mbox format, so the whole problem reduces to getting the NSF content into MBOX, which is a well served conversion. This is the key realization that avoids the Windows and Notes assumptions, aim for MBOX and Apple Mail takes it from there.

The conversion, since NSF reading needs the right tool: an NSF converter that outputs MBOX or EML is the piece and while many run on Windows, the practical urgent path if you only have a Mac is either a converter with Mac support or borrowing a Windows machine briefly to run the conversion producing MBOX files you then move to the Mac. The NSF to MBOX conversion is the one step that genuinely needs NSF reading capability, everything after is native Mac.

The encrypted mail caveat that could derail the deadline: Notes NSF files can contain individually encrypted messages that need the original Notes user ID file to decrypt, and a converter without that ID skips them, so if the NSF holds encrypted mail, factor in obtaining the ID file, the detail that turns a quick conversion into a delayed one when discovered late. Check whether the mail is encrypted early given the deadline.

The urgent path assembled: convert the NSF to MBOX with an appropriate converter, on a borrowed Windows machine if needed since that removes the Mac tooling constraint fastest under deadline, move the MBOX files to the Mac and import them into Apple Mail via File, Import Mailboxes as mbox format. The mail lands in an On My Mac mailbox, done. Under deadline the borrow a Windows machine for the one conversion step approach is often faster than hunting for perfect Mac native NSF tooling, with the MBOX target being what makes the Apple Mail side trivial.