I've had some pups that were big eaters, and some that liked to graze. So what your pup is doing, is not abnormal.
You can try other dog foods, but be sure to slowly add it to the existing food.
Otherwise it will upset his stomach.
When trying a new food. I always buy from a store that I can return it, if it doesn't work out.
I agree that there are tons of different food choices, and just about as many opinions on what food is a better choice.
Not all those who wander are lost.
Life is just a leap of faith.
Spread your arms and hold your breath and always trust your cape.
Two things define you. Your patience when you have nothing, and your attitude when you have everything.