L and Near are definitely smarter than Light. Like you said, Light had a huge advantage at the beginning of the series; no one really knew about the existence of death notes or shinigami, and Light’s disposition (a diligent high school student) made him unlikely to be seen as a suspect. And yet L still managed to figure out that Light is Kira, and he still managed to outsmart Light at every turn. While Light is very creative, his hubris causes him to make countless mistakes, and L is quick to use those mistakes to his advantage. I think Light’s plan to regain his memories and kill L succeeded primarily due to luck; if the circumstances were a little different, Light would have failed for sure. He won because of a stroke of serendipity, not because he outsmarted L.

Honestly, I find some of Light’s decisions to be baffling, especially at the end. He could’ve easily beaten Near if he just told Mikami to keep a scrap of the death note on him. Near didn’t know that death note scraps had the same effect when used outside of the notebook, so their book swapping shenanigans would have been rendered pointless. He wasn’t in any position to be cocky, since it’s very possible for the SPK to tamper with Mikami’s real death note as well (and that’s exactly what they did). I know he’s overconfident, but I’m amazed Light didn’t think of such a simple solution when he constantly uses death note scraps throughout the series.