I just finished the chemistry part of my degree at UNSW so I am probably a very reliable source haha
So in terms of maths, it will just be some formulas-so not very demanding... so maths 2 unit is definitely enough. University chemistry is much more difficult and not at all like HSC chem, in that you will NEVER get a question about impact of chemistry on society, but rather it will just be straight chemistry, whether it be organic chemistry-where you need to work out what series of reactions you need to get to one reactant to the product through multiple steps, or identifying orbitals in atoms or explaining why certain metal-ion complexes binds better than others, you will never get an essay style policy/impact question.
There is usually one lab per chemistry subject per week, and that is around 2-4 hours depending on what chemistry subject it is. Lecturers are varied... like any uni, there are good and not so good (in terms of boring lecturers), but they all know their stuff. In uni, you will find you need to learn at a much quicker pace and beyond first year, there is no tutorials meaning you will need to teach yourself the chemistry homework/do assignments with no help other than from your peers. I had a lot of fun studying chemistry in uni, and I hope you will consider it too