I tend to look at the text I copy and then glance down at what I'm typing to double check I'm on track. But, honestly, I think everyone finds what works best for them - some people don't like that it only highlights the word your typing and not the exact letter.

Hello,
I personnally always look at the text I am copying, because my muscle memory tells me when I made a mistake, I just feel it. Only then do I look at my copied text to make sure I am correcting from the right place.

I strive to only look at the text that I am trying to copy. Looking at what I'm typing might help in the short term but will impede your progress long term.