would i check what type of wireless card a (android) cellphone has
 

I'm interested in knowing what kind of wireless card (a/b, g, or N) my (& my dad's) cellphone has, because if it is N, like all the laptops in my house, I'm going to set my router to just broadcast N (as I've read this would be more efficient if you don't need to broadcast the others).

Is there somewhere in the settings I could check this? (If someone is so inclined, the 2 phones in question are a Galaxy S4 & a Droid Razr).

would i check what type of wireless card a (android) cellphone has
 

You can Google the specs for the phone. A good detailed spec sheet will list the supported WI-FI modes. Or you gan just try the brute force method. Change your router to N-only mode and see if they can connect. In any case, you have the right idea. using N-only mode will be faster than mixed mode. But even if you can't use N-only, G/N mixed mode will be better than B/G/N Mixed mode.