Hopefully, this will help you understand why you get mixed answers:
1. Usually your recipe will tell you a clear SG to rack it to secondary.
2. In older recipes or when making "artisanal wines," they use observation rather than SG. Many winemakers never use a hydrometer. They rely on appearance. This is "riskier," but not much. That is why you might see an instruction to "rack to secondary when active fermentation slows down." When the visible foaming dies back, then you rack. If you use a robust yeast, that time will be very pronounced in your bucket. You will look and go, "Wow, something has changed here!" It is dry. Time to rack. If your yeast is weaker, you may have to really watch for the change time. It does usually happen within 3-7 days, though, and sometimes as long as 10, but not often in my experience. 3-5 days is usual.
3. Depending on the wine being made, some racking is done at earlier than dry stages. There are two phases of fermentation -aerobic and anaerobic. Sometimes a recipe will call for racking over at 1.030 or some other number, because you need to get the must over to secondary for anaerobic work before it finishes out all sugar. If it is called for, do it. Be sure to leave enough head space for active fermentation initially in the carboy. Then top as it relaxes.
4. Most wines are fine being racked to secondary when dry or very near dry.
