YQB arrival would be the small plane - higher B gate number so a long walk to CBP custom hall.

Sat holiday morning, there might not be that many CBP agents if there aren't many intl arrivals.

The Chinese and Nigerian passport holders will be subjected to full processing (prints and photo).

You would need to Google for expected NYC traffic and road closures due to July 4 festivities and guesstimate you chance of making a JFK to LGA transfer. Other factor to consider is what are your options if you do end up at LGA and missed the 10:15am LGA ATL flight.