does aspect ratio determines final video dimension?

Hi,

I have a question about the aspect ratio.

Let's say I used the standard NTSC aspect ratio to create my comps.

When I finshed the AE proects, my rendered movie would be 720 x 480.

Let's say I need to play the movie to a screen with bigger resoluaiton.

Do I need to resize the apsect ratio of all my comps and adjust every elements?

Or, does media encoder can fix this for me?

My concern is 720 x 480 can't really make up extra quality pixels to fill up a bigger screen.

Any ideas?

Thanks.