I have T-Mobile as my esim and I am currently using the Xfinity-Verizon service in the physical sim slot. With an iPhone Xr, you can assign either line to be primary voice or data, so I have T-Mobile as my data line, and Xfi-VZ as my voice line. This prevents the Xfi line from racking up data charges. Both are active for voice and text at the same time though, and imessage works as well. The overall advantage is that I'm getting Verizon voice and text coverage domestically for the monthly taxes & 911 fee (About $1.50 in Oregon) with no per call or text charges while home. Overseas I'll have $.10 a minute calls (Xfi-VZ) all over Europe on one line, and free 256kbps data roaming (TM) on the other line. Free texting on both lines while roaming or home. Another appealing aspect of this setup is, there is no activation fee, contract period, sim charge and even free mailing for the sim card. The Xfi-VZ line falls back to their included Xfinity WiFi network which is quite large locally. It just seems like a sweet deal, but time will tell.

Edited to correct roaming text cost quoted above: I read the details and texting on the Xfi-VZ number is billed per text. This seems to be a fixed $.10 per text incoming and sent. I'll be researching a way to avoid this while roaming if conveniently possible.