I'll round it off with my tuppence worth on HK. Lived here 8 years. Two DC: 7&5.
What is the healthcare like, for example is private healthcare affordable?
Private healthcare is usually included by your employer to some degree but how comprehensive it is massively varies. The public system is also almost free and is pretty good if you're being blue lighted, giving birth or getting vaccinated, but not great for everything else. Is loosely modelled on the NHS and is under massive financial pressure.
How good are international schools with special needs? Do they tend to have Sencos? Not that great tbh. Some are openly selective. Of those that aren't, most will have "inclusion specialists". Both dc have children with statements (ASD/ ADHD) in their classes but either they can cope in mainstream with minimal support or their parents are paying for 1:1 TA support. There is a school called The Harbour School that is more inclusive. Classes v small. It is very expensive though.
What are class sizes like? Around 20-30, depending on the school. Harbour School smaller.
Failing knowledge on the above (which is quite specific I know), what's good/bad generally about living in any of these places? Or advice on best places to research?
Good: Vibrant, high energy city, great social life, diverse expat population, very affordable childcare/help, has seasons, has beaches, amazing countryside and the city all in v. close proximity, good public transport, kids learn mandarin in school, tax is flat 15%, can work on a dependents' visa.
Bad: Expensive, crowded, apartments will be small compared to UK, poor air quality, near N Korea
, traffic bad but I wouldn't say worse than a lot of other Asian cities, socio-economically unequal (but again, not necessarily worse than other Asian cities).