Where do my partner and I start?

My (F24) partnerr(M33) have been together since 2021 but we never made it really official since recently. But over the years, we have travelled together, lived for 3 months together, and even have a business together. He holds a PR visa in Aus while I am living in the Philippines.

We're thinking of Subclass 820 or Prospective Marriage. Which would be easier for us? And which visa has a higher chance of getting approved?

And is it better to avail assistance for the visa lodging?

Thank you.