I think any spinning coaster will be somewhat controlled, so probably not as bad as it sounds, if I had to guess.
I think the concept for the Donkey Kong Mine train sounds intriguing…but I am willing to bet it will actually be a very slow coaster, overall. Having the mine cart on an arm like that will cause vibrations similar to what was often experienced on rides such as the trendy (but pretty much dead) standing coasters from several years ago. The stress put on that arm necessitates keeping the motions very slow and tame. Should make for some interesting visual effects, though, to have the “track” disappear at times!
The rumored “tail” for the dragon themed coaster I doubt will be a reality. They might try it, but I think the stressed on it will probably force them to remove it due to gyroscopic forces. We’ve seen other rides in the past try gimmicky “tails” of various types, but the stressed on them during the rider proved problematic. I believe even Slinky Dog’s tail was swapped out for a fixed tail rather then original concept of one that actually moved.
I do love that they are trying new things, though, and maybe I’ll be wrong and they have those technological issues worked through!