Your summary is right, you get dropped straight into second year and finish honours in three years instead of the usual four. And yeah, it's a bit less flexible in the sense that you have to start working towards a major right away, so you'd probably need to start with only 2-3 subject areas rather than the 4 that most normal BA students would do in first year.
A lot of the slightly differing degree options they offer are more like marketing strategies to attract the top HSC students than things that make a huge amount of difference once you arrive at uni. The BA(Adv) would stretch you a lot in first year, but once you get familiar with your chosen field and get used to the level of work they're looking for, there's literally no difference between it and the normal BA - you're doing the same classes and the same work as everyone else, just you're doing it a year earlier. So I don't really think the post-degree options are much different, because once you get past the first year the two degrees basically add up to the same thing. If you can sell employers on the idea that an honours graduate from an 'advanced' degree is better than a plain vanilla honours graduate then maybe you'd gain a bit of an advantage, but I think most HR people would be a bit more canny than that. They'd be more interested in your marks, particularly your honours mark.
As for lecturing - the pathway to an academic career in Arts fields is the same whatever flavour of degree you do for undergrad. You need a good honours mark, you need to gain admission to a postgrad research program of some sort and work towards your PhD, and when you start applying for academic jobs they'll be making decisions based mainly on your research. By the time you get to that level (or even to honours level, really) the exact type of bachelor's degree you did will be long forgotten.
So overall I don't think it makes a huge amount of difference to your post-degree options. Not that this means it's exactly the same as a regular BA - it's designed to stretch and stimulate the really capable students by enabling them to skip the basic first year subjects and jump straight into the meatier stuff, so if that sounds like it's for you then go for it. But once you get past that phase it's all much of a muchness.
