Definitely do a 3/4, it is beneficial either if you are "motivated" and want to do well in VCE or not.
If you are aiming high I would try to do two or three. It is fantastic to be able to knock a few subjects out of the way in Year 11, very good to share the work load across two years. That's even better if you have done the 1 & 2 component in Year 10.
If not many subjects you can still do without 1/2: BM, Geo, His, FM, Physc etc.
If you are not so bright and arn't someone who is going to get 90+ I would still recommend it. To get the experience of completing a 3/4 is very important, as in most schools it is a lot different then the prior 5 years of schooling.
Many boys at my school did a 3/4 last year and got a score of between 25 - 30 when they thought they were going to do very well. It was a fantastic wake up call and these boys now realise how important the EOY exam is.
2c. MBA.