Revision of large implant results
The saline implants you have now are known to produce rippling and scalloping of the perimeter that can be seen under the skin. Placement below the muscle will help reduce this. Capsule formation is inherent with any implant, but the severity of capsule thickness can lead to deformity or displacement as well as firmness. I would caution you against going bigger because the weight will cause more rapid sagging over time along with back pain and shoulder strap grooves. Discuss your desires with your surgeon and plan to bring in photos of models with breasts that you like as well as what you don't like.
I'm sorry to hear about the problems you are experiencing. Based on the fact you are experiencing rippling and encapsulation, conversion to the sub muscular pocket sounds like a very good idea. Whether or not you will be able to have a larger breast implant utilized and/or require breast lifting I cannot tell you based on the single photograph. In person evaluation would be necessary to give you meaningful advice. You may find the attached link helpful to you as you learn more. Best wishes.
Changing to silicone implants beneath the muscle will probably disguise them better and improve the rippling. The old capsule can be removed at that time. Bigger implants will give you more of a lift. Whether or not you want even larger breasts, or if you want a lift, is a personal choice.