i'm not aware of any research by any reputable historian that suggests that Hitler was not 100% bought into the racist ideology. Hitler's unflinching belief helped doom Nazi Germany, especially when it came to racist view of Slavic people, which quickly turned the war with the USSR into one of racial annihilation, one that Germany would loose.

Napoleon, on the other hand, is almost universally considered a opportunist when it came to religion. For example, he embraced aspects of Islam during the Egyptian campaigns.

Just to make this clear, what do you mean "as Napoleon was a Catholic"?

I've come across this idea many times, and while I don't want to imply anything regarding OP, it often comes from right-wingers. We do not know for sure when Hitler's antisemitism started, but the time when he struggled in Vienna seems like the best possibility. We're stumbling onto a case of cause and effect there: Did he get interested in politics because of his antisemitism or did he implement antisemitism because of his interest in politics?

There are good reasons why it's the first of those two. First of all, from his time in Vienna to his political rise so many things in Germany and Europe changed that he could've easily picked other enemies - the aristocracy, the socialists, the economic elite for example. But he didn't, because antisemitism played a key role in his self-contained world view, that was in huge parts inspired by Houston Stewart Chamberlain and others.

To say that Hitler half-heartedly picked up antisemitism is also making Hitler dumber than he was: Had he picked another enemy, Germany would've done better. While the short-term benefits of expulsing, killing and dispossessing Jews were, in economic terms, beneficial to the Volksgemeinschaft, it (would've) crippled the economy in the long run.