Also check out this thread for some discussion of using MT761x devices: GL-AR300M Shadow 5GHz dongle?
Note that there may still be some issues with these Mediatek chipsets. I am currently testing MT7610U with plain OpenWRT (not GL.inet firmware) so I can’t compare directly to @wcs2228 as I think he is testing MT7612U with GL.inet firmware. But vanilla OpenWRT had some bugs with the MT7610U in version 21, and while it’s improved in version 22, I still haven’t verified a lack of major problems.
I am currently testing an Alfa AWUS036ACHM which is designed for high power and long range, but, it is only a 1x1:1 unit.