Picture attached for reference.

I have a similar kitchen and family room situation. We opted for wood transition that matched vinyl. Glad we did as I know the vinyl would not look so good after all these years. Contraction would have left gap.

I think it looks great! Do you like it?

We once worked on a similar project, where the client was on a tight budget. So we opted for a transition for the expansions and contractions that would come in the near future. Besides, the transition will serve its aesthetic purpose. So, yes, you need a transition piece. Thank us later.

Any added trim will stick up above both floors. Most people would rather have flush transitions. Leave it alone unless there's an issue. It looks great from the picture.

That sure looks like a "bullnose" (finished edge) wall tile being used at the floor. If so, those will fail. If it's all wall tile used, the entire floor will fail (thinner tile). It looks like you have LVP butted up against the "bullnose," where they will expand and contract. You can already see a couple cuts riding up a little higher on the curved edge than the others. A proper install would be no "bullnose," providing a gap at the end of the vinyl planks, and a Tee transition.