Which Airport to use for primary WiFi router, Express or Extreme? I've been using an AirPort Express 802.11n as my wifi router. I wanted to extend my network to another part of my house and someone recently gave me an Airport Extreme 802.11n. It was easy to set up, extending the Express signal, and it seems to be working. 

However it got me wondering if I have it backwards: should the Extreme be the primary base station with the connection to my cable modem?

Also, while I am here, can I use the Airport Extreme 802.11n with Time Machine? There are conflicting reports online.

(I know this is old tech but I am on a tight budget and these hand-me-downs still work well enough for me)
If it works for you there's no need to change. I thought I'd read someone else say that you can't use the ethernet ports to extend from the wireless network on an airport extreme if it's in client mode but I gather you're only using it for wifi and it sounds like it's already working.

You can use 802.11n AE with time machine, from my experience I wouldn't recommend it though. The initial backup was expected to take ~20hrs and it kept restarting. In the end I plugged the HDD into my mac once a week to do a backup instead.