I think I'm looking for a compromise between a plunge bra and a bralette: low-cut, comfy, with a wide band (and wide straps if possible), which won't just spill me out every time I lean over. I prefer one that has to be done up to an over-the-head kind, ideally a sustainable/ethical and/or good quality brand I can buy online.
I'm usually a 36C/34D.