It is possible that they could be relevant on the site, but note that we don't like questions that boil down to one person's opinion versus another person's opinion, or those that are essentially a straw poll. But you can do yourself a lot of favours/harm just by the way you ask the question.
For example, if you want to know about "safest means of transport", I can see nothing wrong with asking if anyone knows any statistics regarding the safety of various formns of transport. Well, except you'd probably also need to define what you mean by "safety". You never know, the question may already have been asked, which will save you the trouble.
However if you simply ask "what is the safest", the way the question is phrased is inviting opinion and anecdotes. You're almost inviting some guy to pipe up and say "cycling must safer than cars because my neighbour's dog got run over by a car".....which has limited value as an answer.
For something like "how much money do you save", there you're lookingb for a bunch of answers, "I save x", "I save y" and so on, and that doesn't fit with my understanding of what this site is about. You're more likely to have some joy on a forum-type site.