Basically these things can apply to a person, but as they get older, it may be harder to tell that they have SPD unless a person is specifically told. People with SPD may act strange or unusual and may not tend to go in the general direction everyone else is going in. However, just because someone has SPD, it doesn't make them any mentally stable or intelligent. They can in fact be extremely intelligent. Their way of thinking may be different and they may occasionally say something unusual or act awkwardly.
Just think of it this way. Take a normal person, mess up their senses, give them a unique way of thinking (which can be good or bad), and then just let em run loose and live their life. Depending on the person, they'll act differently, but in general, they're still able to function. They just may have a different way of living.
I personally have SPD myself, but I was worked with when I was young, so I function a lot better than I would have had I not received that sensory help. Nobody can really tell that I have SPD. Even when I tell them it takes some explaining before they understand it. We can be pretty chill people though, so don't worry too much about it.