T-Mobile Cylinder, pfSense and Google Wifi

I'm using the T-Mobile gateway as a secondary Internet connection at home.  Primary Internet is with the cable company, and the T-Mobile appliance and cable modem are configured as a gateway group on my pfSense firewall.  I use Google access points for home WiFi.  My primary WiFi network uses two Google access points in a mesh configuration.

Unfortunately the T-Mobile device cannot be configured for bridge mode.  I've disabled the T-Mobile WiFi and connected it to my pfSense appliance on an Ethernet port.  As a result, I do have a bit of NAT madness going on.  Direct WiFi speed through my T-Mobile gateway to the Internet clocks in at around 100Mbps, but traffic through my pfSense drops down to ~ 40Mbps.  (I tested direct WiFi through T-Mobile before disabling it.)

Though the T-Mobile gateway is configured as my failover Internet connection, your question got me wondering about external Plex access.  I like to access Plex from hotels when my family is on vacation, but had not tested it out through the T-Mobile gateway.  So I switched my default pfSense gateway over to T-Mobile, disabled WiFi on my phone, and tested Plex access across the cell phone network.  It works.  I monitored the pfSense firewall logs and verified that the client traffic (phone) was coming from a T-Mobile IP address.  I was streaming a Plex movie on my phone while my kids were on the home WiFi using tablets for YouTube, and a baseball game was streaming on a Roku player in the other room.

I realize that my home setup isn't exactly what you were looking for, but hopefully it's close enough to help answer your question.  The T-Mobile gateway isn't flexible enough for me to want it as a primary Internet connection.  But it's been a great secondary/failover option for me.  And for $50/mo it's certainly better than no Internet connection, which is where I used to find myself when cable Internet outages hit.