I've heard that I should ride bareback to improve my position, and ride in my english saddle without stirrups to improve my posture. Does either work better than the other? Or do they improve 2 different things?
I'm not absolutely sure but I don't think they really improve different things though I could be wrong. I think its just more with the saddle that it spreads your weight over a larger area on the horses back then if you were bareback. Also it might be a bit more of a comfort thing like if I ride my mare bareback if I lose balance it can really hurt (because of her withers) and with a saddle there can be more to hold you on the horse whereas bareback there is nothing but your muscles. I hope that makes sense. Hopefully someone else can help you more.
What position issues do you have?
Bareback can be reasonably good for balance, however it encourages you to grip with your knees to stay on - NOT a good thing.
Riding a saddle without stirrups is great for developing your seat and use of your pelvis and back. But again, I would not over do it particularly if you're only starting out in the saddle, as like bareback, you do not want to be enticed into gripping with your knees to stay on.
Well, I am an eventer, but I have problems switching between dressage, and jumping-type (hunter I guess) and I'm pretty much stuck with a dressage-type seat. I hope this makes sense. Anyway, would jumping bareback or stirrupless help that? I need to improve my 2-point is what I'm trying to say.
I'd say that dropping your stirrups won't help in the ways you want it to. Because you don't have stirrups, you are more likely to revert back to the comfortable dressage seat. Think exaggeration with your hip angle in huntseat. You should be leaning more forward than you think is necessary. I did hunters and dressage for years, and my trick was to keep my hips loose so that I could switch easily. That meant a lot of sitting gaits in both dressage and hunt seats WITH stirrups. When you jump do you find yourself left behind?
I think that riding on a lunge line would be great for working on your two point. A problem riders tend to have is balancing in their two point through the bit. Get your instructor or a friend to get your horse working at a consistent pace then practice your two point without reins. Try it at a walk then trot, then canter. Eventually you can add ground poles.
I don't think bareback will help because your issue isn't your seat from what I gather, its your position. Riding in a saddle with help begin to put you in the right place. While working on 2pt to strengthen your legs and core will be good, I also think a lot of exaggerated flat riding will help. Oh and to answer your question, bareback addresses seat, while no stirrups work helps strength. Strength isn't going to help you if you are not comfortable or balanced in a huntseat.