I agree there are a ton of feeds on the market today.
For my part, the one to stay away from, without question, is good ole sweet feed.
I don't care how it's bagged it is the worst thing for a horse since bot flies and tapeworms.
There was a 10 yr period where I was sucked into feeding sweet feed, but a very wise feed store owner sat me down one day and said I needed to re-think sweet feed. That was in the fall of 1998 and I've never looked a bag of sweet feed in the face since :P
The type of feed should depend on the age and health of the horse. Hay, amount and quality of pasture and turn out time are also part of the formula.
When the horse in my avatar went metabolic last year, I took him off anything with oats & corn. I eventually transitioned all four of my horses to Duke's base meal. The only differences are the supplements.
When I did that, I discovered that the snarky personality another TWH has had all his life was directly related to oats & corn. He wasn't even off oat/corn based feed a week before I saw a huge change in his personality for the better.
This is when the "Good Old Days" really were and I miss them. My horses were on 100 acres of pasture they shared with beef cattle. Ate grass hay, oats and corn that we grew,
There was no such thing as hybrid hay, oat or corn seed that was created to fatten cattle quicker but was still used in grain products for horses. I blame a lot of horse health issues on that --- hybrid seeds to produce product to quickly fatten cattle for slaughter.
Coggins didn't exist, neither did any of those other diseases horses need protected against. And that was as recent as the mid-1960's
Sorta got on my soap box -- my apologies