Mum to grace, welcome to the forum.
Do you mean previewing the shared files in the library? Some have a preview but yes a lot of them don't. Provided the spelling is correct I tend to just show everything I download. At times I mute the sounds if I don't like the voice quality, but usually we watch it all once. Then if I or my kids don't like something we delete it or repair it. Since my aim is massive imput I figure it can't hurt to show it. I have yet to find anything that is just plain wrong. I do find the occasional spelling mistake though. ( seriously my family just wouldn't believe that I can even spot a spelling mistake with my spelling history!
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An option to watch them through online once before downloading would be good. But then i would probably rarely show them more than once....
I do recommend you show Lots of files. So just download them and make them work for you through editing features.