Your files look alright here, besides the bleed missing ;)
Maybe it's a hardware performance related issue. I couldn't reproduce the issue with or without the different rendering in the Acrobat preferences (smooth and all) but I suspect Acrobat is "working" on that rendering; try without the smooth line and all the rendering effect in Acrobat preferences in the "Page Display" panel.
Adobe Acrobat sometimes show vectors in a weird way but if you zoom in and it's sharp, it should be alright. And you used vectors, you cannot get a better quality! Your Indd file seems alright, I don't think the issue is there.
If you checked "Use overprint preview: Always", it's actually good for you and you should have this option enabled!
If you get a bad overprint trapping on some of your text or image, you'll see it on your PDF and can fix it (or at least see it if you wanted it this way.)
This is the kind of thing that can happen if you have overprint on some elements.
By having that overprint preview enabled you'll know what's the issue if you wonder why some text seem to disappear or have weird colors. If it fixes you preview issue and maybe other potential trapping issues, that's a double win!