What are the best visa options for an Australian passport holder planning a border run before a February flight from Thailand?

You didn't tell us the date your current stamp runs out, so we don't know how many days you need to make it to February 23rd.

If it's soon, even a tourist visa 60+30 won't get you there so you'll still need to do another run anyways.

If you're going to use an agent, doing 2 border runs between now and then should be fine.

And yes if you're doing a border run it should be 45 days visa exempt with a 30 day extension.

You won't be getting any visa at all as visa exempt means no visa. And the agent likely won't be involved in you getting the additional 30 days as you would apply for that yourself at immigration.