You have to also consider that due to timetabling arrangements, it may not be possible to change throughout the year. This is really up to each individual school, rather than VCAA (at least at units 1 and 2).
However.. i'd say if you want to have a go, try it out in Year 11 and if you find you're struggling you can always move to Further the year after.
Look TBH if it isn't required for your uni course interests, I personally wouldn't worry about methods. It isn't worth you worrying or stressing out over. My gut just by reading this says you'd probably be better off in General, but have a chat with people who actually know you (e.g. family, friends, careers counsellors, even your current maths teacher) and get some opinions as well

I think your current maths teacher would be a really good starting point tbh - they know your current ability and they have your maths data/performance.. so they know your capability (to an extent).