Isquare,

Your iPhone 14 with sim tray should still be able to use dual sim service from either the esim + sim card or dual esim, like the iPhone 13 US model. Will that version of iPhone only run dual sims with 1 sim card and 1 esim? I had a iPhone 13 US model and it worked fine on dual esims.

Or, have you considered just buying an esim from someone like Airalo that roams in Hong Kong and run that as a dual esim with T-Mobile esim when in Hong Kong? Any dual sim configuration you use will permit the IMS function, and allow simulated WiFi calls to and from the US without charges. It's easy to set up and use, and you can practice if you have two lines available for testing prior to your departure. In the States, US Mobile has a $5, 30 day esim available with 500Mb, 500 min. & 500 texts that won't break the bank. It runs on the Verizon network I believe, so service should be reliable, depending on your location.