I'm playing a 9 Int Naga Paladin.
His lack of 'smarts' is something I attribute to his being from a whole different part of the world, and never having enjoyed a formal education. What with being from a nomadic desert tribe and all.
Still, he doesn't get treated as 'stupid', because he isn't.
Is he less smart than most? Sure. Doesn't mean he gets belittled for it. Though that might also be because the party's seen what he does to creatures that earn his scorn. Suffice to say that you don't want one of his Danger Hugs™.

As for RP, I portray him as having a mildly child-like interest in the things that happen around him. Sometimes asking 'silly' questions or misunderstanding something to let the smarter people 'dumb it down' for him, which prompts explanation and deeper thought into the matter.
Which in turn might spark a realization and thr answer for them as they grasp the solution by simplifying the matter for him.

Always remember Occam's Razor. "The simplest solution is often the correct one".
And many a D&D party will overthink and overcomplicate things for themselves.