I recently went on a trip to China (Shanghai and Beijing) and Hong Kong for about 9 days in May 2019.
The trip was splendid. We were a group of 75 people led by our spiritual leader Swamiji Udit Chaitanya. Most of the devotees are senior citizens from Kerala. The weather was very pleasant. It drizzled for a few minutes one day only.
Language is a major barrier as most people there don't understand English properly - even at airports and train stations. I installed an app on my Android phone called Dear Translate that does translation (text and speech) from English to Chinese but couldn't do the other way around (for the Chinese people to use) as I could not locate an option to type in Chinese language on my phone which ironically is a Chinese make (Xiaomi, but bought in India).
Because most of us were vegetarians, we ended up at large (capacity for 75 people to be seated) Indian restaurants which had excellent North Indian food and one non-veg curry. Only for one particular day we went to a Chinese restaurant for vegetarian lunch that served Chinese cuisine which a lot liked but there were a few persons who still preferred Indian food.
As of now (2019), China's Internet has blocked Google's websites, Facebook, Instagram, Twitter, YouTube and WhatsApp. We need to use a VPN like Express VPN and install it on our phones before entering China. Google Play is also blocked so can't install it after entering into China. These restrictions are not there in Hong Kong though.
Even though China is more populous than India, it's not crowded in China like the way it is in India. The roads are all wide and all neat and clean 4-6 lanes like in the Western countries. Since the country is itself so vast, the cities are spacious.
Shanghai :
Mostly a financial city, we first went on an hour long cruise overlooking the city night life in the financial district which has skyscrapers.
Went on a ride on the Maglev train to and fro. It takes 7 minutes to cover 33 kilometers. It's top speed is 431 km/hour. This was really fantastic.
Traveled to Beijing via bullet train which covered the distance from Mumbai to Delhi in about 5 hours.
Beijing :
Unlike Shanghai, Beijing is a much much larger city which would take 6 hours to travel from one end to the other of the city.
We went for a Kung fu show by Chinese monks which was just amazing, though I can't tell if the performers were Shaolin monks or not.
We walked along the Great Wall of China. The steps are high so many elders couldn't climb. Apparently it would take 200 days to walk / climb the entire length of the Wall. Swamiji, myself and a few others (say about 10 of us) climbed up a few kilometers and returned the same way after sometime.
Hong Kong :
One half of the day (evening) we went sightseeing the night life.
Most spent the next and final whole day at Ocean's park which is like Singapore's Sentosa. But some 12 of us including myself cut short the Ocean Park after lunch and went shopping for the rest of the day.
Things you should buy in Beijing :
Buy as many headphones from Beijing as possible - you'll get wired headphones for 10 Yuan (Rs 50) and wireless bluetooth airpods (not Apple's) for about 100 - 150 Yuan (Rs 1500 or less). The smaller stores may not accept credit cards but I didn't check thoroughly.
Things you should buy in Hong Kong :
Shops in malls close at 6PM.
There is a street called Li Yuen street where there are numerous small shops where you can buy a variety of items. Mongkok has ladies market we were told where you can bargain like anything but we didn't have the time to go there since we were in Hong Kong for about one and a half days only.
Hong Kong has a famous electronic store in central called Fortress. Things are cheaper than in India, but I find that Indian credit cards have some cash back offer when using certain cards. This is not possible in Hong Kong. I saw an iPad Air 1TB version for $15,000 HKD which is about Rs 1.33 lakhs.