The wireless settings you have should work fine in most environments. You might want to change the Roaming to low or medium low, however, it may not account for all the performance difference you noticed.
It would be good to check with the router manufacturer if there are any firmware updates for the Access point.
For testing purposes, you may want to disable the Bluetooth adapter and check if that improves the WiFi connection.
Also, check if you get better results changing the position of the PC, or placing it close to the Access point.
Faulty antenna on the zenbook, or the zenbook has some programs that conflict/take away bandwidth . BTW 16 MB/s (that's 128 Mbps throughput FYI) is the norm for N connection so there's no problem on the other asus with 7260. I get about 50 MB/s (400 Mbps throughput) on my laptop connected to 802.11ac router.
I am having similar issues on my work laptop. I work from home for the parent company and have a PolyCom IP phone connected by wireless bridge plus a host of other devices that work flawlessly with my Netgear Rangemax WNDR3700 router. My Dell Latitude with dual-band 7260 simply will not stay connected to the 2.4ghz. side of my router. I have to go to the 5ghz. before the connection is solid.
I used the Intel Wireless Event Viewer in real time to view events while using the connection utility to connect to the 2.4ghz. wireless radios on the router. The connection consistantly goes into roaming, authenticating, roaming, authenticating pretty much non-stop. This makes for a very slow / sporadic connection whereas my Fonality HUD drops offline/online/offline etc.
When I use the same method to connect to the 5ghz. radios of the router, all is good. So there is definitely a problem with the 2.4ghz driver pack for this card. I believe it is in the authentication/security side as the logs on the router show WLAN denial requests because of authentication about every fifth attempt.
Security is set to WPA2 Personal PSK/AES - again, no problems from the 3 Roku boxes, Xbox 360, XboxOne, PS3 or iPhone/Pads in the house. Just this machine and 7260.
So, you are NOT crazy....