there is a fb group that is very knowledgeable about all that is car seats in australia. ( Child restraints. Is your child restrained correctly? )

i think the goliath is same as the nobel and also the custodian, just different badges.

older seats are weight based. most 0-4 car seats have an 18kg weight limit forward facing. do you still have the manual to check?

different seats absurdly have different heights to switch to booster mode. Also, some older models have lower switch heights than others (same seat but different covers).

i think the law says that children must be in 5 point harness car seats until at least 4 years. the only exception is if they are too big for ALL car seats on the market, not just the one that you have.

car seat research drove me crazy! i kinda wish i had got a convertible booster for DD, rather than a booster, so i could keep her in harness for longer plus not having to try to do buckle up (in booster) when there is a seat next to it. i do prefer the Vario to the hi liner. dh has a hi liner in his car.
I think I have decided to get the Nobel for DS and the some sort of Infasecure booster for DD - she passes that 5 point test thingy and finds the strap between the legs uncomfortable - she is not tiny so I can see why. I like Infasecures stance on the harness situation - e.g. they acknowledge the research about the problems with using additional harnesses. Which Vario did you get? Is hard to see the difference between say the Kid and the Caprice apart from the colorful covers?