@ARGamingPK1 

Hi, firstly(Off topic), the moderators might not be constantly online,  particularly on weekends. We always appreciated users helping users for a prompt response. It might not always be helpful. But the general guidance is based on their own experience, official FAQs, Chat Database, and various other official resources. If it is not related to the posted issue, you can skip the reply and tag the moderators for assistance. Even responses from moderators may not always hit the mark, and you can request further escalation to the engineers since certain queries may exceed our expertise. However,  overall respect and appreciation would be highly appreciated.

Thank you very much.

Best regards.

  @ARGamingPK1 

And back to the transmit power, for US versions, the FCC permitted the WiFi Transmission Power to be <30 dBm. So 26dBM is still within the range.
Wider channels, like 40 MHz, occupy more of the limited spectrum and are more susceptible to interference. Reducing power for 40 MHz channels helps manage this. Additionally, wider channels can include more noise, and lower power assists in maintaining signal quality. This also helps with compatibility for older devices that use 20 MHz channels.

If there are multiple smart home devices, it would be better to keep 2.4GHz on 20MHz.

As for the side effect, I saw several Google searches mentioning that high power can cause devices to remain connected to a distant AP even when a closer one offers a better connection, hindering roaming in multi-AP setups.

Thank you very much.

Best regards.

  @David-TP So i should keep using 20 MHz with lower Transmit Power like 20 dBm on all Deco units? Does is affect Mesh Technology of Deco Units? Or i should keep on 40 MHz with Low Transmit Powers? Can you suggest me Transmit Powers for 5 Deco Units at 500 Guz house and 500 Guz is equal to 4456.8 Square Foot which is almost 1500 Foot. Please suggest for both 2.4 GHz and 5 GHz for band 4 channels. Can i disable 2.4 GHz WiFi Backhaul i did that 2 days ago but the Satellite Deco Units was using 5 GHz for Backhaul but the signals are medium or weak. But the performance on all Deco Units was far better because all the Deco Units are using different 2.4 GHz channels.

  @ARGamingPK1 

Hi, I'm afraid there isn't a clear reference on how many dBm is suitable for a specific wireless coverage.
Honestly, as you have Deco units, running field tests in your own network situation would be more efficient.
Based on the previous user feedback, 20MHz usually works better than 40MHz. It is worth a try to disable the 2.4GHz Backhaul if it has no obvious side effects on your current mesh network. Many beta firmware versions for other models to improve the smart home stability have also disabled 2.4GHz Backhaul.

Thank you very much.

Best regards.

  @David-TP Hmmm that's right i will disable the 2.4 GHz Backhaul and then i will shift to 20 MHz with Lower Transmit Powers because Mesh Units on 5 GHz Backhaul work better than 2.4 GHz Backhaul but the signals are Medium or Weak on 5 GHz so i should keep the 5 GHz power to 25 dBm.

  @David-TP Finally i have disabled 2.4 GHz Backhaul and im getting Medium Signal Strength on all Deco Units and this is my Speed Test Result on First Floor Bedroom Deco which is connected to First Floor Lounge and i think this speed is good on my 100 Mbps connection.