I have tested the 'N' by uploading video via ftp. A 2gig video file took around 13-15 minutes. 3 Users uploading the same increase the upload to around 25 minutes. Channel Bonding didn't improve the upload for some reason, but then again.... my client didn't have 'N' supported devices. With the gigabit ethernet, you should see better performance anyways. If you are using the 2.4GHz you shouldn't channel bond anyways. On the 5ghz you can..... So depending if your devices support 802.11a or 802.11b/g, then that will tell you how many ap's you can put in a single room. 2.4ghz, you really can only go with 3 ap's, if your clients support 802.11a, then you can add more ap's, but just disable the 2.4ghz when you reach the 3 limit.

First you must find out what type of client devices you have and what standard the devices support.