I don't think it's all that weird or jarring because there is a variety of looks. And actually even Kili has some facial prosthetics, a little bit on his nose, Turner mentioned it in a couple of interviews.

You have the really Gimli looking dwarves and then there are like different levels. Thorin, Kili and Fili look the most like little men, Ori and Bofur are very recognizable as the human actors who are playing them, they don't look that much different even with the makeup, so they are just sort of like at the next level of dwarf looks from Durin's line. Dori, Nori and Dwalin are probably up on the next level, Bombur, Bifur and Balin on the next and then Gloin and Oin.

I don't understand the reasoning on changing Fili and Kili from being the youngest to Ori, given it was an important reason for their physical characterization even in the books, they could see the best, were the most dexterose and nimble, etc but I don't think Ori is much younger, Kili and Ori are basically the equivalent of older dwarf teenagers and Fili is like just his very early 20's being 5 years older than Kili.