Airport extreme's WIFI speed is less than half of the Ethernet speed(Bridge mode)

Theoretical max speed at 5 GHz for the now obsolete AirPort Extreme is about 500 Mbps. But, that's theoretical. Remember that WiFi is Half-Duplex, so the actual throughput speed is going to half or less than the theoretical transmit speed. So, call it maybe around 200-250 Mbps best case for WiFi speeds.

By now, you might be thinking that there is lot of good old fashioned lying when it comes to WiFi performance claims...and you would be correct.

So, your figure of 190 Mbps is not bad. The AirPort is at least 9 years old and as much as 11 depending on when it was placed into service and some significant fall off in performance would be expected after 6-7 years of use.

If you have the time, you could experiment with different WiFi 5 GHz channels manually to see if your guess might be better than the guess of the AirPort Extreme.......(which is supposed to take a look at available channels and choose the best at the time).

Otherwise, I would not spend much time trying to figure out if some other "magic" setting for the AirPort might exist. For a 9+ year old product, it is doing pretty well.

For 2.4 GHz, I would avoid Channel 1 unless there are very few other WiFi networks around you. Most routers default to Channel 1 for 2.4 GHz, so it is typically the most crowded channel. Try using 6 or 11 if you want to set channels manually.