Nice Menu Font Size

Hello folks.

I installed and got to work the nice menu module.

I toyed with its CSS to see how to change the colors and found out.
However depending on WHERE I place the Block, the font size of Nice Menu is very different.

So I wondered where do I have to make a change for changing the font size of Nice Menu ?

In its own CSS ?
In my theme CSS ?

When Nice Menu Block is set in "Featured". It's far too big and large. How do I shrink that ?
Then when the Block is on "Highlighted" , it's much cleaner.

Thanks for any hints !

Thanks !