How do you fit the very important character of Man-Ape into a movie without making it horribly racially insensitive? For starters, you don't call him Man-Ape, but use his given name, M'Baku — and then you give him a primate mask anyhow, just in case no one made the connection to the comic character. The hulking warrior from the comics does clash with T'Challa pretty often, but just like in the MCU, they're able to put aside their differences now and again. In the comics, it was for Black Panther's wedding to Storm.
As for the triceratops-looking mask that Killmonger decides to steal from the museum, it's doesn't have an exact comic book counterpart, but it does bear some similarities to a mask Killmonger dons in ritual combat in 2008's Black Panther #38, inasmuch as it has two kinda pointy things on it. But mostly, the MCU's Killmonger is a far cry from the comics, diverging in both goals and backstory, even though both enjoy taking off their shirts. Mercifully, comics Killmonger's penchant for beating people with a spiked belt is also not on display in the MCU.