Changing channel on airport extreme

I have been reading that switching the channel from Automatic to a set number channel might help reduce interference etc.

I don't want to discourage you from experimenting, but that technique is not likely to be successful for very long, if at all. If you leave the channel settings on "Automatic" AirPort Base Stations can search constantly and relentlessly for the channel with the best throughput. Limiting it to any particular channel will prevent it from doing that. Meanwhile, changing your channel will only encourage your neighbors with their wireless devices to change theirs, perpetuating the neverending battle for limited wireless territory.

To answer your questions though:

My questions are: do the 2.4 GhZ and 5 GhZ channel numbers need to be the same as each other on the same router (meaning if I set the 2.4 to be channel 6 on the Airport Extreme do I also need to set the 5 GhZ on the Airport Extreme to channel 6)?

No, in a roaming network they need to be different. Besides, the 5 GHz network uses higher, differently numbered channels. Channel 6 belongs to 2.4 GHz.

To address Wi-Fi problems please read Check for Wi-Fi issues using your Mac - Apple Support. The Summary page at the end, the one containing "Review Wi-Fi Best Practices", is likely to suggest some actions for you to consider.

I have been reading that switching the channel from Automatic to a set number channel might help reduce interference etc

That might be true in theory.....IF....you somehow knew what the "best" channel to use might be at any given time. Let's say that you decide that Channel 11 might be a good choice.

So, you would need to use a WiFi utility to look at all the available channels in your area....to make sure that other routers were not already using Channel 11. Assuming that they were not, you could then manually switch your router to use Channel 11.....and things might be OK for a few hours......until other routers that automatically scan available channels decide that they too would like to use Channel 11.

So, in a few hours, you will need to scan again using a utility to try to find another "open" Channel, which will soon be occupied by other wireless routers around you that are always scanning to look for a better channel.

If you really do have a few extra hours each day to manually try to look for open channels and then choose them, it's possible that you might do OK.....but.....it also very unlikely that would do any better than simply leaving your router on "Automatic" and letting the router do the work for you.

There is much less interference on the 5 GHz channels, so if your devices are capable of connecting at 5 GHz, that would be the way to go.

There is a real downside to 5 GHz though....and that is that 5 GHz signals are much weaker than 2.4 GHz signals, so 5 GHz is only going to work well when devices have line-of-sight to the wireless router, or they are in close proximity to the router.