The honest version, so nobody books the wrong thing.
It is nose-to-tail. Horses follow the horse in front on a set trail, led by a wrangler, at a walk. Some operators will allow a trot on a suitable stretch with an experienced group; most will not. This is a liability structure as much as a riding decision, and it is standard across the state.
You will not choose your horse. Ranches match riders to horses by weight, height and stated experience. Tell them the truth at booking — an experienced rider on a plodder is bored, and a nervous beginner on a forward horse is unsafe.
There are weight limits, and they are enforced. Published limits on Oʻahu ranches have commonly sat in the region of 230 to 250 pounds, and riders are weighed or asked to confirm. This is about the horse's back, not about you.
There are minimum ages. Trail rides typically start around seven or eight years old. Gunstock's pony rides cover the younger end, roughly two to six, and are a led walk rather than a trail ride.
It is hot, and it is dusty or muddy. No shade on the pasture at Gunstock in summer; deep mud on the valley floor at Kualoa in winter. Both are normal and neither cancels a ride.
Rides are short. Sixty to ninety minutes is standard. Two hours is a long ride here. If you ride regularly at home, book the longest option available and set your expectations for the landscape rather than the riding.
What you are paying for, then, is an hour in country you cannot otherwise get into, on an animal, with somebody who knows the ranch. Judged on that, it is worth it. Judged as riding, it is a walk.