How powerful is Draco's wand

Why does the elder wand belong to Harry?

You don't have to "own" a wand to master it. Since the elder wand was considered to be the most powerful staff, of course everyone hunted down the respective supporter. That's why the first rumor spread that the owner had to be killed. You just always killed that person, so no one noticed that normal disarming was also possible. That means EVERY disarmament. Because disarming is considered a defeat. No matter which staff the wizard now wields. But you never knew that beforehand.

It is similar with the property itself. Of course, the winner of the duel always took the baton. Why not, they wanted him. Draco is likely to be the first to own the staff, but never actually took it. Instead, the staff was buried (according to custom) with Dumbledore. Whether Draco has it with him or not, the wand's magic recognizes HIM as the true owner. When Harry finally disarmed Draco again, the baton passed to him. Even without owning it again.

Nor is the elder wand comparable to any wand in this regard. In principle, a magician can do magic with any staff. But there is just the one where you can get the best possible result with little effort. It has something to do with the personality of the wizard and the nature of the staff.

The elder wand is very different. He IS the perfect staff for EVERYONE and the most powerful of them. Therefore it has these special magical mechanisms that you have to "earn" it. The magic then prevents anyone from using the staff. See Voldemort.

Draco's normal staff doesn't really obey Harry, but Harry can do spells with him because it's a normal staff. He has earned the Elderwand and magic accepts him as a master. The stick could be lying somewhere on the ocean floor while Harry is on vacation in the Andes.