Later today I will revisit your thread with more detailed comments on your question.
But for now, your following comment caught my attention, that is
Both can do the same thing it seems, apart from the fact that time remap can ramp in and out
Premiere Elements Time Stretch Tool can also be used for "ramped slow motion". Have you seen the YouTube video tutorial on the subject?
But I would make the distinction in my comments to follow about the easy of use as well as the absolute can and cannot do aspects involved.
To be continued.
Also Time Stretch is applied overall to a clip, while Time Remapping can have several time-shifted segments, each with its own specs, applied to a single clip.
Time Remapping is also a more sophisticated tool with some excellent frame blending capabilities so that even greatly slowed motion will look smooth and natural.