Set up images export to fit both horizontal and vertical screen in ePub in InDesign

Couple items and a question or two. First for kindle, only ever use previewer to test the ebook, past couple years amazon has moved away from saying to test on devices or apps besides previewer, their recommendation, so I'd do that first. Second, so the first image you posted, vertical and horizontal in your original post, when you flip it horizontally that's what you will see, the image will have the white space on the left and right, because it can't fill it entirely unless it's a more horizonal image. For amazon also remember, nothing too fancy for them, to them a dropcap high styling, so just a word of warning. Your image looks like it is also seetup to be centered and space above and below so that's where the text will go. This could have been done in indesign or if you altered any css afterwards. But let me know if you are looking to accomplish something else in case I misunderstood what you want to do.