I had a TB mare for many years, and used hoof boots on her for 12 years with her. I found that after the initial transition from being shod, she was fine with being turned out and ridden in the ring/arena barefoot. The feet do toughen up.
But I still used hoof boots for most trail riding. In my experience, the only thing that really matters is that the boots fit. That may seem like a no-brainer, but, as you may have found out, it’s sometimes hard.
My preference, because of that, was for boots that came up over the back of the hoof; in particular, I used the Easy Boot Back Country–but in their initial version. I know they’ve changed the model and I don’t have any experience with the new version.
The boots that cover more of the hoof and heel bulb tend to stay on a little better and are easier to use throughout the hoof trimming cycle without you having to do some rasping yourself. They may not be the best choice for certain types of riding (endurance perhaps) or certain types of terrain. But on western Mass’s stony trails with frequent muddy streams, they were great.