When can I JUST use TM internet modem as ONLY a modem, in BRIDGE mode, with NO NAT, NO firewall, and frankly NO Wifi.

OK -- Sounds good, but let me ask to confirm a few things:

-- I'm assuming then that your mesh router is providing the DHCP so that is the device that is handing out the IP's?  This is critical, since it was at least reported that the DHCP was limited to 20 dynamic IP's internally.  I assume then also, you are at least ignoring their WiFi and using only yours.

-- Someone else mentioned that it did NOT support IPv6 properly. Going forward this will be more of an issue than it is today.

-- Double NAT -- There are a few people I’ve heard that had significant issues, since this caused some services to be rerouted

-- Static IP's and port forwarding -- There are many reasons and situations where this is critical.  For instance, I've got some very old devices that I need to reach on demand, some from outside my network, on the internet.  If I can't predetermine the IP's for these devices, AND specify which ports and traffic is routed to them, then these devices will not work, or will be randomly unavailable.

-- Bridge Mode -- The reports that I heard that originally caused me to ask / report these issues, is that they said it would NOT support bridge mode.  This means that their device must first be configured, and then if you are "lucky" or brilliant, you can force your router to UN-do the TM router, and then apply it's own settings.   

-- How do you overcome the requirement for bridge mode?  I know in the past with several home WiFi routers that wanted to add their own NAT, DNS, and DHCP, if you didn't disable DHCP, DNS and enforce bridge mode, you just couldn't get your devices working properly, nor could you get these devices all on the same subnet.

Each problem I mentioned above have caused a lot of work to overcome at some point, which is why once you get everything set up, you really do not want to make any changes to your network.  Some problems are just virtually impossible to easily overcome.  Even today, I've got an old "WiFi CELL SPOT" with T-Mobile firmware.  It's a fine WiFi as long as I only use bridge mode, do not use their firewall, NAT, DNS, DHCP etc.  But, that firmware will NEVER EVER be updated by T-Mobile and the hardware vendor, NetGear.  But then, since they support BRIDGE mode, there's no problem, either.

REALLY, let me know, or someone else can report these issues.  The only reason I'm writing this is that I WANT to see this working easily and reliably.