desync and unexpected disconnection

your internet speed has nothing to so with the stability of the connection OR the latency. It's merely a measure of how "fat" the pipe is.

think of your internet line like a water pipe. if you have a 20mm pipe, it won't allow as much water through as a 50mm or 1m pipe, right? that is what bandwidth or speed tests measure. how large the pipe is. there are other factors at play however. just as a pipe can have a large diameter, it can also have a long length. just as the length of the pipe would slow down the "latency" of the water, a long connection increases the network latency (among other factors).