WiFi throughput depends on the placement of your router and connected WiFi adapters, i.e., the position of their antennas.
I just tuned my WiFi, by testing various placements and observing the detailed signal quality in real time using the following bash command,
while sleep 0.5; do clear; iwconfig wlan1 | grep -iE "rate|quality"; done
which will continuously output the data rate and signal quality of your WiFi adapter wlan1. Note that, depending on your setup, your device name may be different, e.g., wlan0, wlan2, etc.