T Mobile is 5G and most work on 2.4. I found out that Nest is 5G and 2.4, so it should work. I'll order from Amazon on Cyber Monday.
I think you are confusing and mixing terms. Wi-Fi radios operate on different frequencies. For awhile people used letter designations like B, G, N, etc. Then it become more common to see 2.4ghz or 5ghz. Most recently 6 and 6E is the latest and greatest. Each band offers different advantages. For instance 2.4ghz is going to be slower (about 100mb max) but often has an extended signal range. 5ghz is faster (about 400mb) but typically doesn’t have as large a coverage footprint. So sometimes when going through walls, long distances, etc then a 2.4ghz is preferred because it’s more stable vs faster. And depending on the device you may not need maximum speeds. As point of reference 6E is getting close to 1gb wireless speeds in optimal conditions.
But again, these are the radios that allow devices to communicate with each other.
The 5G that T-Mobile offers is referring to speed. How much speed is up for debate but generally it’s what I classify as high speed. I have T-Mobile phone service and under 5G is also 5G UC (which means ultra coverage). The latter is faster than the base 5G. To my knowledge T-Mobile doesn’t charge for UC, it’s more of like you are closer to the hub and get a stronger/faster signal.
For reference, I have 1gb fiber up/down at my house. It currently feeds to an older Eero wireless system that I dislike. The Eero’s are only capable of max 5ghz speeds, so around 400-500mb max in real world wireless. I understand marketing hype says faster but it’s just that….marketing. So while my ISP pushes me 1gb service the most I can get through my Eeros on wireless is roughly half.
Now the Eero allows me to setup a Wi-Fi network based on the 5ghz or 2.4ghz bands. I typically keep my less secure devices and guests on the 2.4ghz network. Some devices such as video streaming I keep on the 5ghz network for increased speeds (less buffering). To get my max 1gb speed I currently have to use a hard wired connection. And while many of my devices are 6/6E capable, their speeds are throttled by the Eero 5ghz ceiling. They make new Eeros that are 6/6E capable but I dislike and going a different route with a more sophisticated setup.
For fun, I ran some speed tests at my house. Where I am located wireless strength isn’t great and using my 1gb fiber connection I pulled about 200mb down and up. I switched to my cell service (T-Mobile 5G UC) and pulled about 335mb down but only about 3mb up. The fastest cell service I ever got was when I lived out of state in a large metro with Verizon’s version of 5G UC on the iPhone 12 Pro Max. It pulled over 1gb down in the parking lot of Chipotle while we were picking up dinner. That was crazy fast and the best speed test I ever got. In that area I got others that were 800-900mb consistently but that wasn’t typical for Verizon as a whole as their normal 5G was around 500mb or so.
Hopefully this provides some clarity. Big takeaway is T-Mobile 5G is line speed. The 5ghz and 2.4ghz of each device you are worried about is talking about radio frequencies. You can run a 2.4ghz radio on T-Mobile 5G service; however, as described above the max speed will be less than if that device had a 5ghz radio. However the advantage may be increased coverage range.
