Asymmetry of the breasts is extremely common. Although there are ways to improve symmetry, many times they come at the expense of scars. When it comes to droopiness of the breasts (called ptosis), there are some women who clearly do not need a lift, those that clearly need a lift, and those in between. Although difficult to say for sure, you seem to be in between. In these circumstances, adjusting for asymmetry could mean doing an augmentation with or without an implant. In general terms, is you use a smaller implant, it’ll be more difficult to get an aesthetic looking breast with a close cleavage. You can compensate for that by erring on using a larger implant. As for symmetry, it’ll depend how strongly you feel about it and the trade-off between having scars and symmetry. Hope this helps, good luck!