If you go for Residence under SMC based on your present job, after it has gone through, you will be entitled to do anything (legal) in NZ - run your own business, take any job (skilled or not), study, or do nothing if you could afford it. The only time any condition is normally placed on Residence is when it is based on a skilled job the applicant has not yet worked three months in, and then the condition would only be that s/he must worked three months for the named employer - going back to INZ with proof that that has now been done and s/he is still employed there will get a new residence visa sticker with no conditions. At that point, s/he could then (depending upon notice in line with the contract) leave the employer.
If you started work with your present employer upon arrival, you have already done the three months, so should get residence with no conditions.
The only other thought that occurs to me is that, factoring in processing times for SMC, and that INZ don't prioritize applications for people already legally working in NZ*, you might not get residence till well on towards the two years on your WTR, at which time you would get PR if you stick with it.
*(Many people have waited and waited, not hearing anything, until almost the time when their previous visa would run out. When they write in, saying this, Residence appears in an amazingly short time. So we draw our own conclusions.)