If you'd like to try a bra you must consider that a regular bra enhances the breasts while a crop top flattens them.
So with more tight-fitting clothing a crop top might be the better choice.
Yes, you are right! The first picture in your group, the crop top looks very much like the magic gravity bra that I wear when I want to be discrete. We can wear them (crop top style) and stop the bounce and sway some that will be a lot more noticeable without wearing anything.
I also use a minimizer bra when I want the full support with very little enhancement, however these bras are much harder to conceal. My big problem is, I have the big double "D"s so they can't be concealed so any bra that stops the swinging and bouncing is a blessing alone!