Hoping I could get some advice on this similar situation next month, I'm booked on EWR-SEA-TPE in J on EVA (BR 25), and TPE-HKG in Y on HKA (HX 253).

Any clues on what I should expect for transiting, US citizen as reference so above article makes it seem straightforward since I'm not checking a bag?

Will be joined by another friend who is doing EWR-MXP-TPE Y on UA and TPE-HKG Y on HKA, however they are checking a bag and also wondering about that process (also US citizen).

Thanks in advance for any advice!