You will most likely make it from TPE-HKG on 22 but you'll most likely be staying in HK airport until 23rd night to get out of HKG as everyone will be trying to get out of HKG for the long Christmas break (HKG 2 days public holiday, Christ+boxing, China-nil)

PEK-HKG on 26 is definitely a no-no, everyone will be trying to get back on that day to start work the next, again the TPE on 27 shouldn't post much of a problem due to the high frequency

VERY IMPORTANT NOTE!
Any China-HKG run on KA & CX are usually overbooked because
1. There is a lot of business dealings between China & HKG
2. Trying to ship 0.0001% of 1.3 billion people is not easy
3. Everyone in HKG prefer to fly KA & CX as chinese airline service is not up to international standard
4. China gives only limited landing rights
5. As a result the ticket prices are always close to full price (at least when I buy a couple of days before heading to my meetings)
6. Some fear the chinese airline safety (not me)

I've only done 2-3 china flights these years on ID (also because my company pays for my trip and also I'm there for a meeting which means a fixed deadline)

Its not impossible but I think your risk is high especially during long holidays. Load out of HKG should be fullish starting from 19 and peak on 21-24. 25 planes will be empty leaving HKG and full on the return until 1st.

I would suggest flying from SZX, you can book some dodgy chinese airlines (especially the early morning ones) they come in very cheap. Safety wise, I think its acceptable.
From HKG, there are direct shuttle buses from Kowloon to SZX, which takes about 2 hrs, from airport, take the Airport express train to kowloon station. go downstairs and take the express bus

Just checked on ctrip, szx-pek still around RMB1,000 per leg, quite ok