802.11n is called HT mode for 7260. The "Wireless Mode" actually functions as disabling one of the bands. By selecting a/b/g or a/g, you enable both 2.4 and 5 GHz bands but your 7260 won't be able to establish connectivity with 802.11b protocol if you select a/g. Selecting a only results to 2.4 Ghz being disabled and selecting any other options without the "a" will disable the 5 GHz band.
Hope this helps. To show if you are connected to wireless N, go to command prompt and type this code
netsh wlan show interfaces