You can certainly go on a WHV but, as you know, it will only give you a year. For a longer stay you would either need a WP (but that would mean you'd have to work for someone) or PR. For PR you would need to see how many points you can get without a job offer. I believe, once you have PR without having gained points for a job offer, you can please yourself who you work for. If INZ gives you a
Work to Residence visa instead of full PR, which can happen in some cases, you would need to get a job offer to qualify and you'd have to work for this company for 2 years, I think.