If you get within eight weeks of the expiry of your WHV, then the normal thing would be to contact the CO, to point out that your current visa is expiring on that date, and to ask if your Residence is likely to be through in time, or if you should apply for a work visa to keep you legal. (If you don't have a CO by that point, or one has only just been allocated, then it will be obviouis that you need to get a work visa.)
You'll have gathered from that that no, you aren't covered to stay in the country if your WHV runs out. Someone who has applied for a work visa will automatically be covered by an Interim visa
https://www.immigration.govt.nz/new-...t/interim-visa in that situation, but those are only available for temporary visa applicants, not those applying for Residence.
You need to be careful to be legally covered by a visa of some kind, because if you became illegal, this would stop processing of your application under SMC.