I'm not a twin, but my best friends all through secondary school were twins. They were (and still are) very close. They shared a bedroom, clothes, underwear (their elder sister shared pants too, just one massive drawer of them, I found that weird but I have a brother so never shared clothes). They were completely different personalities. Even though they were identical, I found it easy to tell them apart. We're still friends now and my DH doesn't believe me that they're identical as they are so different in every other way so he can easily tell them apart.
They disliked being known as 'Twin'. As PP have said, some people didn't even bother learning their names. They dressed differently as much as possible, though school made that tricky, so one chopped her long hair really short. They and their sister had allocated colours as children, for towels, water bottles etc. Never bothered them, and it ticked over into the teen years. They were in separate classes initially, but in secondary school ended up in many of the same. Some classes I'd have with one sister, others I'd have with the other.
I also nannied identical toddler twins. Parents keen to treat them as individuals. I did like dressing them in coordinating outfits though. Think the same plain t-shirt in two colour. But put one in dungarees with it and the other in shorts. Despite being identical genetically, one was stockier than the other and never looked quite right in dungarees, whereas his brother rocked them. You might find that with your boys, one simply might not suit something. My children (not twins) had similar with dungarees. DS1 just didn't suit them. DS2 looked awesome in them.
I know people with multiples that lay them on a particular side for pictures, usually in birth order so you can tell who's who.
Fascinating thread though. Thank you.