I fly a lot between HEL and CAN, with AY. Though the only-summer schedule by AY was quite frustrating, the now opened high speed railway HKG-CAN really save the day, I have done it three times. (All reaching CAN downtown by noon)

time break down,

morng arrival 9am HKG,

HKG airport to West Kowloon railway station by metro(HK) airport express, 24mins

West KL(HK) to CAN(south) by highspeed railway, max 60mins, departure every 30mims or so.Fastest one is a no-stop-47mins reaching CAN (10am everyday, given AY arrival in HKG and transfer in Metro, not likely but doable if you are lucky, becoz u need 30mins spare time doing cross border passport contro only one-time in West Kowloon HK to enter mainland China)

Reach CAN(south) before noon anyhow.
CAN(south) is suburban region of CAN, going to CAN business center by metro or taxi, depends where you go, max can be 1hr though.

The whole journey reaching downtowm is less than 13hr, maximum. And the high speed railway is also pleasant.

(Remind you if you fly to CAN by CA or CX via stops, let say, min 14.5hrs not considering delay time inside China, which is quite common, the airport of CAN is in CAN(north), from there to CAN downtown also takes 40mins, def more than 15.5hrs in the outmost optimal scenario, and usually can be way longer. In this sense, high speed railway is so much punctual than air flight)