sizing objects

Hi all...
Just wondering the best way to make a collage of sorts. I want to put 
several images into 1 image, and wonder:
1. Will I get better sharpness or smaller file size if I resize the 
objects to the final size first, or can I just resize them when I import 
them into the new image.
2. If I import them 'on the fly' rather than pre-sized, is there 
anywhere that shows me the size of the object? I can not find that 
anywhere. I want to make sure there is consistency to the object sizes.


Thanks in advance!
John