How realistic is scoring a first/business class ticket from Xi'an → Beijing HSR ticket on May 1 via Trip.com?

First-time China visitor here. I'm planning to take the Xi'an → Beijing HSR on May 1 (yes, I know, Labour Day).

The situation: 12306 releases tickets 15 days in advance, which puts my release date at April 16. I'm planning to book through Trip.com rather than 12306 directly.

I'm flexible ±1 day (April 30 or May 2), though my current itinerary has me leaving Xi'an on May 1. I realise April 30 might actually be worse since that's peak outbound travel day.

My concern: Trip.com acts as an intermediary, so I assume there's some lag between 12306 release and Trip.com availability. For a first-class seat during the single busiest travel window of the year — how much does that lag actually matter?

Specifically wondering:

• Has anyone successfully booked a Labour Day first-class ticket through Trip.com, or is 12306 basically mandatory for high-demand dates?
• How fast do first-class seats on Xi'an → Beijing actually sell out around May 1? Are we talking minutes or hours?
• Would I be better off just wrestling with 12306 directly + a Chinese phone number?
• Should I just skip the HSR gamble entirely and book a flight now? Flights are bookable immediately and I wouldn't need to stress about release windows. Is that the smarter play for Labour Day, or are domestic flights equally chaotic?

Open to any "here's what actually happens" takes. Thanks!