"It looks as if the split screen method is best, as one can then see what one is moving over, except for the fact that, this only moves them over. "
Using this method, the default action is COPY if you drag to another drive and MOVE if you drag to another location on the same drive. So this should work perfectly well for you.
If you want more control, you can use a right-drag (i.e. using the right button instead of the left); when you drop (release the button), a menu will pop up offering Copy, Move, or Create Shortcut.