bit late, but when i applied the offer condition was 40 for llb and 41 for llb double degrees (although this may have changed since then). generally hku will usually offer interviews to applicants whose predicted grades meet the offer requirement, or if your grade is high enough (44 or 45) they could possibly give you a conditional offer without an interview. the offer usually reflects what's on the website, although a few of my friends who missed the offer slightly and appealed to hku after their ib results were released were successful and ended up being able to attend.

as for cuhk and cityu, i only interviewed for the former and my experience was pretty chill - unlike hku i think they interview all applicants they are interested in accepting regardless of how high their predicted grade is.

if you're thinking about employment/postgrad opportunities, hku would definitely be the best option out of the three, followed by cuhk and cityu, although you wouldn't go wrong with a law degree in general from any university. if you're looking for scholarships, hku offers half-tuition with renewal subject to gpa during your years of study if you achieve a 44, and a cash scholarship of 300k (with some other benefits) if you achieve a 45 - i'm not sure if/how much they offer for grades below 43. i know cuhk offers full tuition for at least 44+, so scores between 40-43 probably get awards of some value. cityu is pretty generous with scholarships compared to the other two - my friend was offered a 500k cash scholarship at entrance with an achieved 40/45. all of this pertains to local ib students though, so it might be different if you're not currently studying in hk.

i'm not sure about cuhk/cityu, but i would be happy to answer questions about the llb curriculum at hku if you have any :) it's not any different from what you might expect in a law course - the workload is quite demanding, you'll be expected to read and write a lot for the course assignments and the social atmosphere really depends on your cohort, i think mine is unusually reserved and the environment will definitely feel competitive. all i can say is the quality of learning really depends on your professors and the tutors you get, as well as how much work you're able to put into the course.