Page size is adjustable while formatting a drive. Once a drive is formatted, you will not be able to change page size except by reformatting it.
Larger page sizes will mean that any file (or part of file) will always take that much space on your drive.
For example if you have a page size of 1MB, a 3.1 MB file will be saved in 4 pages as 1 + 1 + 1 + 0.1
The last page will have 0.9 MB wasted.
On the other hand, accessing the file will be faster as only 4 pages have to be read (as opposed to more, if the page size were smaller).
Hope this helped!