I experimented with powerline network adapters for a while. You might see 400 megabits on the same circuit. Between floors in your house on different circuits? Very unlikely. The latency was also pretty bad compared to wifi.
My experience is also that between floors (circuits) you loose bandwidth.
With latency I see no issue and I find that weird.
Latency, with Wi-Fi or not, it’s probably correlated with transmission failures so there probably some bad circuitry or devices than create noise (like electrical motors).
My experience with powerline adapters is that they all fail sooner or later... I think 230 V is just too much to handle in a small package combined with sensitive low voltage communication chips.