The key to treating the lips with fillers and volumizers is to create balance and proportionality between the upper and lower lips (and the chin). In general the upper lip should project forward about 1-2mm more than the lower lip in side view and the volume ratio of the upper lip to the lower lip in front view should be 1/3 to 2/3, respectively. An expert injector with extensive experience in performing nonsurgical lip augmentation with fillers will keep this in mind along with the projection of the chin in order to avoid creating duck lips or trout lips. The point is to make sure that you get examined and treated by an experienced injector and insist on seeing his/her before and after photos.
Lip Augmentation is easily accomplished through proper selection of product and product placement. Lip augmentation is both an art and a science. You are an excellent candidate for lip augmentation. For a thinner look you can have Restylane injected or Belotero. Juvederm will give you a more pouty look. Please consult a board certified dermatologist with a great deal of experience with fillers to achieve the best cosmetic results.
Thank you for the great question and for sharing your photos. Hyaluronic acid fillers, such as Juvederm and Restylane, are a great option to increase the appearance of "thin" lips such as yours. As long as you are clear with your surgeon regarding your goals and concerns about having too much filler ("sausage looking lips") I wouldn't suspect that you would have a problem with that. I do not believe you would be a candidate for any lip lifting surgical procedure at this point. Good luck! and thanks again for sharing!
While you do have thin lips, you have a nice shape to them. I often recommend starting with a temporary hyaluronic acid based filler such as juvederm or restylane. These fillers last around 6 months and can provide volume to the upper and lower that can be very natural appearing. The "sausage" appearing lip examples that you don't like have a lot of filler in them and represent somewhat of an extreme example, in which I agree are overdone and don't look natural. Injection technique is also crucial to providing a natural looking lip augmentation and avoiding the "sausage" and "duck" lips. There are many people with lip fillers walking around that you wouldn't even know have fillers in their lips and that's more likely the look you are going for.
You do appear to have a long upper lip, so a subnasal lip lift is another possible option if your goal is to shorten the upper lip and give more red lip show to the lip. This typically effects only the central 2/3 of the lip. This is only an option for the upper lip and will give a more subtle volume enhancement.
A lip lift only affects the central third of the upper lip and is a not a procedure for the lower lip. Only a lip (vermilion) advancement can change the amount of vermilion show from one lip corner to the other without making them look too plump or protrusive.