Recommendations Genius MC.

The MC is not even as smart as 2 of the side characters (Xuan and the other kid who keeps pulling his hair out) so idk what you're saying. He even admits that he's not a genius.

 

NOVELS
Genjitsushugisha no Oukokukaizouki - Wouldn't say "Genius" but MC isn't naive and he makes hard choices for the better good (Little bit like code geass)
Dungeon Defense - IDK if genius , but MC's only strong point is knowledge and scheming
I am the Monarch - MC is "Genius" because nobody else can think of basic tactics in this novel
Overlord (LN) - A little bit paranoid but mc (especially if we include his minions) is scheming for the most of novel.
Isekai Mahou wa Okureteru! (WN) - Genius MC (magic wise)
Mondaiji-tachi ga Isekai kara Kuru Sou Desu yo? - I would say smart enough MC ? well its up to debate but hes cool headed so it might be why i think hes smart
Seiun wo Kakeru - MC has a lot of knowledge of futures technology if you can call it smart
MANGA
One Outs - Genius MC so its something you should check. (completed too)
Kaguya-sama wa Kokurasetai: Tensai-tachi no Renai Zunousen - Two smart leads female and male , tries to make each other fall in love due to their believe that first one to admit is loser or something like that, (Great manga if can enjoy school slice of life with romance)
Isekai Yakkyoku (There is novel too) - Genius related to medicine and healing reincarnates into fantasy world
Isekai Tensei Soudouki - Has two souls within him, One is Japanese? another is some general so he learns a lot of stuff
Kurosagi - Genius swindler, he lost his family or something like that due to swindlers so he now swindles swindlers (Yo dawg i heard you like swinders so we are going to swindle some swindlers why they are swindling others)
Vampire Juujikai - You can say MC is genius (MC reminds a bit of lelouch )

Thats all i can think form the top of my head (thought some of them aren't "Genius" you expect)