I have never known one to be trained out of being gaited for riding, as that is one of many reason most people want them. They have one of the smoothest gaits I have seen. I have never seen one jumped, but I believe any horse can jump if they have the desire to. I have seen some hotheads within the breed, but they have been few and far between. They are a breed with plenty of speed at the rack but they have willing temperments and seem eager to please. To get that rack when riding one, which is a ways off for you right now, you have to be able to help them balance to maintain the gait. Since RMH tend to be on the smaller side for horses I try to wait until the fall of their 3y/o year to start riding. Between now and then just lots of groundwork and bonding.
I use to always ride a friend of mines RMH when we went trail riding. I wanted one forever but never found one that was not priced for a zillion dollars (exaggeration) and then ended up finding minis instead, but that's another story.
You know how to make a miniature horse even smaller? Leave them in the dryer a little longer!
"Don't ever regret something that once made you smile"