Your right. There are lots of different opinions on deworming so you'll have to read a lot and make as informed a decision as you can.
My own view point is that if your chickens are on the ground they can get worms, period. Just like any other animal that is on the ground. DE and ACV are not dewormers and will not keep worm loads under control. Chickens can be full of worms and not show any visible signs until their health is in decline. At that point they have a lot of damage from the worms and their health is compromised. Far better to stay on top of the situation rather then let it get to that point. Fecal tests can be done but you have to do them often and they are usually not free. My own avian vet charges $50 a pop, not something I'm going to do on an ongoing basis. A random fecal test done only every few months or a couple times a year can easily give a false negative. I have found that the easiest, most effective, as well as cost effective, way to control worms is to simply deworm my birds two or three times a year with a good, broad spectrum wormer. I use Valbazen and liquid Safeguard for goats. How often you deworm depends on your climate. It's fine to deworm in the fall or early winter when laying decreases anyway and then again in spring/early summer. That usually keeps most people out of trouble but those in warmer/wetter climates often have to deworm more often.
So that's my 2 cents, I'm sure you'll get many more opinions lol!