Hi Vicky
I'm a diagnostic radiographer who got my visa in December and moving over to Oz in August. We are going over on a 189 visa which meant I had to get my skills assessed with AIR(Australian Institute of Radiography). This was a fairly straight forward procedure. I had to provide the syllabus from my degree and transcripts, evidence of CPD, CV, and references. I believe they require you need 12 months experience for this but I am not 100%. I'd possibly contact them as they were really helpful throughout the process and really approachable.
On top of this you need to gain APHRA registration which is the australian equivalent version of the HPC. I left this till last until after i'd received my visa which was a mistake. It's probably a good idea to start this process somewhere within your visa application as it's taken mine 6 months and hoping to have jumped through the last hurdle and hopefully finding out the results in the next few weeks.
I know this doesn't answer alot of your questions however I only know my experience and your probably best speaking to a Mara registered agent to talk about your options for visas. They often give you a free chat about visa before trying to sign you up to them. Do your research as there are some sharks out there and make sure they are Mara registered.