choppy velocity

Retiming plug-ins are not magic tools. Your source footage likely already has issues when you captured it from Roblox. Making sure a consistent framerate is captured from the start is the first thing to do. Other than that check the footage interpretation and the composition framerates. People always get this wrong and then wonder why Twixtor miscalculates the interpolated frames. Also consider turning off GPU acceleration. The warning sign on the effect is a clear indication that there is either a mismatch in bit-depth or the GPU stuff isn't working correctly. That aside your subject doesn't lend itself too well to retiming. The motions are already choppy (intentionally) and things like fire effects throw off the rest of the interpolation.

Mylenium