People who attended the party were funny. Failing any qualifying context, i would understand that all people present were funny. To say "some of the people" or "many of the people" or "most of the people" would clear this up. I would be inclined to say "Several funny people attended the party." Without a qualifier, "Funny people attended the party", might allow for the thought that not all were funny, but it would depend on the manner of delivery or context if written. I would feel some ambiguity without more context. "Funny people attended the party and told jokes that kept the rest of us in stitches" is clear. "People who attended were funny" seems like all were funny or begs a qualifier. The "three decisions" question is unclear to me.