I have done all sorts of close up work and true macro/micro (1:2 to 2:1) in the past.
Slightly longer lenses do have their advantage in not having to get as close to the subject. A good macro lens will be flat field lens as well as being able to get up close enough.
As most will note, auto-focus is really not a good plan for macro work so getting a lens you can manually focus or put on a rail system makes sense. Thus, older manual lenses tend to be good fits if you want used (cheap option) lenses.
Ideally, a good review would be available on the lens and hopefully provide information as to which f-stop(s) provide the best sharpness and contrast. You may find a macro lens that is sharpest at 5.6 but most know you might want to be in the f/8 to f/16 range and thus that lens is not optimal. In the days of film cameras it wasn't that uncommon to see lenses stopping down to f/32. Usually, f/16-22 were used to have both sharp and less chromatic aberrations.
Last - While I don't sit in the camp of buying FF lenses for cropped sensors just because one day I might* go FF, macros are a different story given that tripods are used most often and one ends up using just the center of the lens. Ideally, a longer lens will come with a tripod mount to help support and balance the lens on the camera.