I dont play to the degree where a +1 modifier is changing how I RP, but thats just me.
Its less the +1 it gives and more how the numbers compare, I would consider a 13 smarter than a 12 even if both only give a +1 mechanically. However the higher you get, the more drastic. At 16 I would consider you very smart and above I would consider it getting more extreme cause 20 is the point in which you'd be considered "perfect" in that stat and at the human limit (Barbarians I think get to go past at level 20 so thats them going beyond the human limit.). So if 16 is smart, 17 is a genius. 18 is either a delver into magical secrets or a walking encyclopedia. 19 is walking library of knowledge. And 20 is, if I don't know it, I will soon enough. They can get more specific like if I play an Artificer that could be more applied to his specialty. But this is just personal and I wouldn't say I stick hard and fast to that
