I saw this on site to confirm.
"A visa is not required for this destination for a stay of up to 90 days. Please keep in mind that while a visa is not required, you must:
Hold a passport valid at least six months on entry with one blank visa page
Hold proof of onward/return flights
Hold proof of sufficient funds relative to your intended length of stay
Hold documents showing proof of purpose of trip
Hold all documents required for the next destination
Confirm with your airline that boarding will be permitted without a visa"
How accurate is this? Do you need to show entire itinerary and just credit card or what exactly?
The information you found is generally accurate. US and Mexico citizens do not require a visa for stays in Hong Kong of up to 90 days, provided they meet the entry requirements. However, Hong Kong immigration officers may ask to see documentation to satisfy them of your travel intentions and ability to support yourself during your stay.
Specifically, you should be prepared to show:
In practice, most visitors to Hong Kong are not asked for extensive documentation. Usually, passport, onward ticket, and credit card are sufficient. There is no strict requirement to show your entire itinerary, though having hotel reservations can be helpful. Always confirm with your airline before departure to ensure they will allow boarding without a visa, as airlines have their own policies.
Additional tips:
Overall, entry is usually smooth for US and Mexico passport holders, and extensive documentation is rarely required unless the officer has specific concerns.