For my home internet, I’m pleased to have municipal fiber optic broadband in my city.
I don’t know what the width of the bottleneck is or where it’s located (because there will always be one) but i have never hit it.
I also use T-Mobile for my cellular data.
They were fairly straightforward with me about how it works:
The data transfer bandwidth will never be throttled by ‘decree’,
though it is finite and everyone connected to the same signal tower as I am are all going to have to share whatever is available
up to the hardware limitations of the mobile devices themselves which are connected.
however, after I have downloaded approximately 10 gigabytes of data, my pings are to be de-prioritized. If there is not a lot of activity on the network, then connections establish in a snappy and responsive manner. If there is a lot of network traffic, however, I may have to ‘wait my turn’ while other people who have not downloaded as much get to go first, to an extent. Once the connection is established, the speed of data transfer is just as fast as before. It just takes longer for that connection to be established in the first place.