I don't have experience in measuring signals or anything alike, but after swapping my ISP router with a Mikrotik hAC3 that my Wi-Fi range has been decreased by a lot.
After some investigation I got to see that --in front of the AP-- my ISP Router had a strength of around -15 while my hAC3 was at -30.
Mikrotik Wireless Package tells me this is the maximum I can legally get (I cannot decrease the antenna gain and it will complain if I try to), while my ISP Wi-Fi remains a lot stronger.
Why is that? Is it that I'm placing my antennas badly, Mikrotik has to update legal limits, My ISP has legal advantages...?