Classic Shell, does change the way that Windows Explorer works in some ways, I found that it improved usage of Windows Explorer to the extent that the folders don't jump up and down the screen when you open them.
As to why your why your destination folder was larger then the one you copied... When you finished was the content of the folder, the same as the original folder or did something else get copied into it?
If the content appears to be the same, look at the individual files and see if any of the files got bigger.