Well, as pacifiers (pacis) are made for babies and toddlers (unless were talking NUK 5) all pacifiers will be small for an adult, even for a small adult. Therefore the largest baby pacifier will be closest to the most desirable size. This is usually 12months+ or something similar. Different brands will differ both in sizes available and in shape. NUK make the amazing adult-size 'NUK 5', which is almost worshipped around this community, but is expensive and must be ordered online. Other threads will contain more info on those, and other members can provide more info, because I don't own one. NUK offers size 1,2 and 3 baby pacis in stores I believe. Baby pacis differ in shape, for example, some animal face shaped ones I had were slightly bigger because the ears shape sticking up a little, so maybe compare a few in the store when buying, if you choose to buy.
The pacifier needs to be comfortable in your mouth and at the same time satisfy you.
No dentist or orthodontist is going to endorse the use of pacifiers by people past infancy. I was 26 and had been urinary incontinent for years before I discovered the benefits of AB. Immediately I rushed out to buy a set of pacifiers. Then as I was boiling them as the instructions said, I started thinking I had just finished two years of adult braces, which treatment took much of my spare cash. Did I want to risk the alignment of my teeth?
I held off trying a pacifier. In DPF, which was a snail-mail ABDL club back then (1990) I saw a letter from a member living near me who admitted being a dentist. Immediately I sent him a letter. He actually phoned me a week later. As an active AB himself he had experimented with several then popular pacifiers. The huge adult NUK 5 were not yet available. The dentist asked me if I was sensitive to latex and I answered that I avoided latex. His suggestion was to try the MAM clear silicone orthodontic pacifiers for toddlers 6+ months. If I could keep one in my mouth long enough to satisfy me he felt it was the least risk of damaging the alignment of my teeth.
I bought such a pacifier set and still prefer the MAM products. The mouth shields have improved ventilation but the clear silicone orthodontic nipples are found in most stores at low prices in many colors. Of course I have tried most of the pacifiers made since 1990, including the NUK 5. For me the larger nipples do not improve my satisfaction. So for me there is no benefit in the risk of a larger nipple. I can see if your teen set back from your lips more. Also, I wear my MAM clipper to my collar, expecting it will fall out of my mouth as I fall asleep.
The best thing is to be careful how often you use a pacifier.