Wirless G or N?

Okay Wireless N is the newest wireless and is the fastest available. It usually gets better signal because it has less interference, and can travel farther.
But if a device is NOT wireless N compatible, it wont pick it up at all, it well have NO internet so you would have to get a new card for it that is wireless N compatible or stick with G. Also some routers have the ability to broadcast on N and G in that case your newest one well run at the faster N speed and the other 2 would be running on wireless G.

For the printer, i do believe if you can print over the network it should have a ethernet port on the back of it to connect a ethernet cable but im not exactly sure.

Well then yes it would increase your internet quality for everything using the N broadcasting. Things still using the G wont notice as many effects.
However most N routers are high end, therefor broadcast much stronger and well give you much more signal. Basically the more you pay the stronger the signal and speed well be.

I recommend Mikrotik routerboard using routeros or some Ubiquity device (e.g: bullet M).

The apple routers seem good, I'm actually mac certified and the ones we use at work seem to do well. As far as a G device not picking up on an N router, don't know if I've heard of that. If they are certified as 802.11g, etc. I'm pretty certain they are designed to be backwards compatible. Keep in mind however, a G card may work on your N router, it's not that you will not get any signal, but your devices will work at the slower G speed.