There is a lot of myths out there about arrows. I have been shooting for over 40 years, probably 50 now and I have seen a lot of "facts" and "fads" come and go. Bottom line is you need to have a properly spined arrow shaft for the bow you are shooting. Over spine is fine if you are shooting a compound with a drop away rest, shooting off the shelf or with a long bow/recurve, then you need to be concerned with over spine. Under spine will cause flight problems as well as accuracy issues regardless of type of bow used. Broad heads need to be sharp, brand doesn't matter, they all kill... if you put the arrow in the "boiler room". Brand of shaft doesn't matter, use the one you prefer. Make sure they are all the same weight. I have shot a lot of different brands over the years and have my favorite. In time, with experience, you will too. Fletching type, style and count is a personal preference. Just use enough fletching to control the arrow. Helical vrs offset is also a matter of opinion and preference, both work well. Put enough helical or offset on the fletch to control the broad head. More only slows down the arrow and doesn't add to accuracy. FOC is another thing to look at. Follow the Easton Arrow recommendations, they know what they are talking about. More than 15% FOC is also a matter of opinion and preference.
Archery is a highly opinionated sport and everyone feels they are an expert. I suppose, for their likes and dislikes, they are, but for everyone else... well, that is the beauty of the sport... you get to wade through all the B.S. and decide what is fact and what is fiction. Listen and read every thing you can, just don't believe it all. Find something that works for you and stick with it. Practice is what makes you good, not equipment or tune. Consistency is key. Enjoy the journey.