Are you sure you uninstalled it for the installed content tab and are you sure you uninstalled the right NEW CAS PROJECT ? (I would just uninstall them all).
As for your question: No, the featured and most downloaded ones are not necessarily safe. The best indication is always the file size. The smaller they are, the lesser are the chances but it would only take one, so that is just an indication.
What I recommend for people who don't want to (or can't cause they are on a mac) is to install one sim after the other. Always check your launcher in between. The newest installed stuff is always at the bottom of your launcher (that will mess up when you close it). I'm a little unsure if that is still true with the newest update but you could always try.
