A little update and report for the 'Maximum Speed' or 'Maximum Coverage' options in the firmware (using 380.57.5).
Environment:
Commercial building (about 40K SQFT).
RT-AC68U
N class client (laptop) on 2.4GHz band
through 3 exterior walls (brick) and one floor at a distance of 30 feet to router.
4 interior walls (drywall) and one floor and a distance from over 80 feet to router.
In 'Max Speed' mode, there was very iffy connections at both distances, needless to say.
Through the exterior walls and from the basement floor (30'), the signal connection fluctuated from 2Mbps to 0Mbps to 12Mbps (as per Windows), depending on how I held the laptop. A stable connection was possible it seems for seconds at a time and with steady hands a couple of minutes were possible to at least 'keep' the connection alive.
Through the interior walls and from the basement floor (80'), the signal seemed much better (an indicated 24Mbps or more), but a stable connection was not possible, even for a few seconds.
In 'Max Coverage' mode though, things were dramatically improved.
Through the exterior walls and from the basement (30'), the signal reached as high as 144Mbps, but couldn't sustain that (indicated) connection rate. But a still respectable 56Mbps was indicated and even reached as high as the low 80's. Even better, I didn't need to be balancing the laptop on one hand to get a better signal.
Through the interior walls and from the basement (80'), the signal actually was an indicated poorer performance (12Mbps), but the connection was stable and fast enough to initiate an RDP to a server and thus made it possible to get real work done.
I would love to know how this magic is done? Can anyone comment?
@hggomes?