I would generally avoid feeding grain unless there was absolutely no better option. If I did feed, it would be well processed(micronised or such) and fed in a large number of small meals daily, mixed with forage/chaff. I would not feed sweet feed or other 'junk food' at all, except as an occasional, tiny treat.
If a horse needs 'condition', if her teeth are OK, she's healthy & no ulcers, worms or such, free choice grazing/hay with part being alfalfa should generally be adequate. Appropriate supplementation for nutrition is important too. If the horse needs more than that, mixing some oil, oil seeds, such as linseed or such, or adding some soy or copra meal or such can be good.
At any rate, if you're confused about conflicting opinions(if you ask a question of 4 different horsepeople, you'll get at least 8 different answers!
), I would suggest you find an (independant of feed co's)equine nutritionist to ask, to learn the factors that effect our opinions. The mob I use and can recommend are feedxl.com