Im pretty sure it’s a thing of the past now, is it still good practice to contact credit card companies when flying internationally?
Never done that for Ukrainian and Polish cards, however EQ bank blocked all transactions in Ukrainian currency. Contacting their support didn’t help
I used my Neo World Elite last August in Puerto Vallarta without issues.
As a precaution I would lock the card via the app until I knew I was about to make a purchase, this way if there are any attempted unauthorized transactions (which can happen in many countries) they would be blocked until I unlock the card
Depends on the credit card company. All Canadian banks typically have very 
experience even if their systems are smart enough not to autoblock you when traveling. I recommend contacting them before traveling to unsubscribe from their services because if ANYTHING goes wrong – you forget your pin, lose your card, buy anything unsusual, get the card stuck in the ATM etc you will likely spend hours trying to get support. None of the banks seem to have good real time messenger support and calling internationally can be blocked or expensive.
Neo is great in most countries but there are countries where it simply doesn’t work, which is why it’s a good idea to have a shitbank as a backup option. Here is the list of unsupported countries: Using your card while travelling | Neo Financial Help Centre
With Neo you 99% won’t need support but if you do you might get stuck waiting for chat, which is another reason to have backup options.
I try to have cash and many cards from different banks and networks (Visa/Mastercard) because something always goes wrong if you travel often enough.
How quickly was the card unblocked and then used? I wonder if there is a lag that can lead to the card being declined at the POS.
I wonder why the Cathay World Elite Mastercard is the only card that can be used in China?
Might have to be that Cathay Pacific is a Hong King-based airline with a large Chinese ownership stake. Furthermore, Visa/Mastercard is generally not accepted in China unless you link it to a wallet like Alipay or WeChat Pay.