As you adjust the spline the object aligned to it will adjust itself to reach the next keyframe. You might want to try keyframing the “position” to get your timing down.
Well, that all depends on what you are trying to accomplish. Not every solution requires high poly counts, normal/bump maps work great and keep render times down.
have your cranked the samples in the dome light? try going from 64 to 256 and enabling de-noising. Assuming since it’s in premiere then its an animation?