As obj already stated, the uploaders are different and each will filter the data differently before sending it off to the servers.
What is common though is the datasource if you are using dump1090-fa for example.
That will put out beast-data on 30005 which all feeders will connect to without the connection ever leaving the computer. (local loopback)
The opensky and adsb-exchange datafeeders just forward that beast data directly to their servers.
Obviously those use quite a bit more bandwidth, aound 25 kB/s for 1600 messages/s.
FA bandwidth depends less on message rate but more on how many aircraft you have in view.
Typically 1-2 kB/s i would guess.
FR24 is in that same ballpark, but that depends a lot on how many other feeders are picking up the same aircraft.
Once a few receivers of theirs receive an aircraft, they tell the other receivers not to send ANY data bout that aircraft. At least that’s what the log looks like, as obj said it’s closed source.
Then separately the MLAT process uses some more bandwidth than mentioned above.
It should stay well below the bandwidth of 25 kB/s for all messages though, maybe half or a quarter of that.
Depends on the mlat client and number of mlat aircraft.