I flew out of the new TAO a few weeks ago, overall very similar look-and-feel to PKX, although a few things that they still need to work on after they've had a bit more time. In summary:

• A long way out of town, but easy metro connection, even if it takes a while.
• The tech looks good on the surface, but still lots of manual intervention - e.g. agents coming to help you as soon as you approach a "self check-in" kiosk.
• Automated passport/boarding pass check had a reader for passports, but foreigners were directed to queue up for a manual check anyway. To be fair, 80% of passport readers I encounter in China don't work anyway, so manual is a good option.
• Security: they have the great theory of parallel loading, so you don't all get delayed by the one clueless person... Same format as LHR T5 and T2, can't remember if PKX has the same. They don't automatically send anyone with a powerbank for secondary screening (ahem - Daxing), but they did trigger secondary screening on the trays for both me and my travelling companion anyway, but then didn't seem to have any specific concern to investigate. Not sure whether that's some issue with their scanner or just the standard Chinese racism to send the foreigners for secondary.
• Departure area and gates: again similar to Daxing, big spaces, long walks, good range of retail. No Luckin, only Starbucks, so Daxing wins on the good value coffee. Gate close advertised as 20 mins before departure.
• Pushback was near enough on time.

So overall, pretty good.