Okihara,
Re. CASA license to RAOz, the answer is yes, simple and straightforward.
Re. medical, the Class 1 is always the place to start, because you never know, you may in the future want to progress to higher licenses, even if you have no intention of an aviation pilot career.
I don't recall if you mentioned where you are, geographically, but go have a look at the nearest RAOz schools, sadly these days for GA, they are often the more active, vibrant and generally just fun places to be, like aero clubs of the "good old days".
A final piece of advice, as you are starting to sound like you have already subconsciously made up your mind to buy an aircraft, re-read all the advice as to why you shouldn't, and if you do, keep the aircraft for your own use, forget the blandishments about how you can defray/minimise costs by hiring to a club or school.
Some of the posters on this thread have been around a long time, "been there, done that", and have seen a lot of tears (and $$$$) shed ( some their own) over the years.
We speak from experience. And CASA is only making it harder and harder, everything to do with RAOz is closer to common sense, far less bureaucratic at all levels and as a consequence, more simple and as a result, cheaper. As well as generally a lot more fun.
The difference in setting up and running an RAOz flying school, alone, compared to CASA Part 141 or Part 142 is probably a factor of 10, maybe more.
Tootle pip!!