It all depends of a couple of points:
1 - Are you here for a Disney vacation?
2 - Do you want to see other areas of Hong Kong?
3 - Your hotel budget.
If you are planning to spend most of your time around Disneyland, then I would suggest staying as near to Disneyland as possible. On the other hand the closer you stay to down town, then the cost of hotels increases big time.
I would suggest that you look into, The Panda Hotel in Tsuen Wan.
https://www.pandahotel.com.hk/
I have put up plenty of people in the Panda, and for the location and cost, it is great! I would suggest you check the cost with your local
travel agent, but do also call the Panda that you are staying for three weeks, thus get a better cost. Trust me it would be worth the cost of a phone call. The Panda is near to Disneyland, and connected to the public (MTR) transportation. This (cheap) public transportation will take you anywhere including Disneyland, that you would ever want to go in Hong Kong.
Another area that you might like to check out for a hotel, is Tung Chung. If you want help for me to suggest a place there, I would be happy to help.
Please stay away from the tourist traps in Hong Kong, I can help you with a list of many places to see, some off of the beaten track, but still on the MTR public transportation line. If you have a list, post it here and I would be happy to tell you about each place.
I'm a western guy who has lived in Hong Kong for over 25 years, and I live in Tsuen Wan myself. Let's have a coffee in Disneyland, I go to Hong Kong Disneyland twice a week. I could even help you with some tips and tricks how to make your Disneyland vacation a little more special.
Check back here often, tomorrow or Thursday I will go and start posting every menu of the park. You will then have some idea what to expect, and what to budget. Hong Kong Disneyland does not allow any food of any kind or any liquid into the park. I would NOT suggest AirBnB in Hong Kong. Take care at Christmas, all Magic Pass (Annual Pass) are block out except one.
Cheers: