@ManhattanMarc 

Low is 50% of the antenna power, the middle is 75% of the antenna power, and high is 100% of the antenna power.

Thank you @Tony. I just spoke to technical support via their live chat and they indicated that on the 2.4 GHz band, high is 20dBm, medium is 15 dBm, and low is 10 dBm. As this is a log scale, these values translate to 100 mW (100%) for high, 32 mW (32%) for medium, and 10 mW (10%), for low. The 5 GHz band emits slighlty more power with the high being 23 dBm (200 mW).

Do you think this is accurate? I had my old Verizon FiOS MI424WR Rev. I Wireless Router 2.4 GHz antenna set at "1%" meaning 1 mW and it worked fine as it was a small apartment and only needed to go through one wall at most. Others confirmed and use this power level as well (100 times less than the default 100% (100 mW).

@ManhattanMarc 

Those mW numbers check out when using a converter.

I've seen a couple of cases wherein lowering the power, better performance was achieved. Not every time, but it has worked before.

@Tony 

Thank you. Yes, the percentages you supplied are accurate when applied to the non-linear log 10 based decibal scale:  20dBm (100%) , 15 dBm (75%) , and 10 dBm (50%). As the log scale is exponental, the absolute power amounts decrease signficantly more: 20 dBm  = 100 mW (100% = baseline), 15 dBm = 32 mw (32% of baseline), 10 dBm = 10 mw (10% of baseline), So the "Low"  power preset on the transmit power setting is actually 10 times lower than high power.  I believe this is correct, especially since  10mW is plenty usable and I have used 1 mW fine in 1 bedroom apartments on routers where you can set the precise percentage of 100mW.

I think in large highrises, like the one I am in, where dozens  of people are within 400 feet of each other (the range of 802.11ac at the 100 mW defaul high power transmit setting), and all using their own WiFi router, it is probably better if eveyone uses their low power setting for a lot less channel interference and lower radiation overall. But I can only control my antenna :o(

Thanks Again for you help.

-Marc

@ManhattanMarc I can't find on where to lower the transmit power on my interface.

Do I need an older firmware in order to do that?

@APPe Not sure, it depends on your router and if it is controllable. If the setting is not there now, it was also not likely there in prior firmware versions.

@ManhattanMarc found it on the firmware interface. Need to click on the Wireless Advanced tab first in order to see it. Firmware is current (Jan 2022). thanks again.