Two things. Does the Wii zapper remote make playing the game alot easier?

Gameplay with the wii zapper to me gets much worse

And if you want big time kills just make sure you have the mp40 in your class,bouncing bettys too

Both of your questions vary depending on how you like to play the game.
If you would rather have a sense of actually holding a gun, try the Wii Zapper. In my opinion, the zapper makes it harder to play.

And depending on what you like doing (sniping, close combat, etc.) your best custom class will change. I prefer custom classes to be more like snipers.

1. In my opinion the wii zapper makes the game awful, pointing and moving on one setup is just way too hard.

2. As a starter I'd use an SMG, like the MP40, then as you level up and unlock more, experiment to find what works best for you.

I don't know what the wii zapper is like. But for the class, here 2 class tht are best.

1:mp40, flamethrower, stopping power, and martyrdom
If you don't have flame thrower....
2:mp40, bouncing betties, stopping power, and martyrdom

Have fun!

Oh I almost forgot. Use the dual magazines in the mp40 attachments