Screensavers are over-rated, and unnecessary - and many of the 'free' ones come with adware/spyware attached.
It's far better to just have the monitor turn itself off when not in use.
Screen savers were required years ago. They were necessary so that damage would not occur on the screen if the computer stayed on the same page for an extended period of time. With today's technology things are changed, no damage will occur if the computer is not turned off and there is no screen saver.
Ask yourself this, why would a company provide free screen savers if there were no benefit to them.
Good luck
I cant give you a definitive answer, but if it were me I would not download from any of those sites. You may want to try Microsoft to see if they have any sort of screen savers.