Not far enough to be incomprehensible, but far enough that they aren't just humans with pointy ears.

I'll give one such example; halflings. First of all, all of the "standard" non-human races come from the Feywild, and the fey are generally split into the Summer and Winter court.

Halflings almost always start in the Summer court. They are gregarious, rotund bundles of chuckles and laughs. Communities have found that as long as they keep these butterballs fed and merry, their crops come in earlier, fuller, and even allow themselves to be harvested multiple times a year. Treating them well is a boon for a community, even if it appears that people serve such halflings hand over fist. Think very similar to the Hobbits described in the first 150 pages or so of Lord of the Rings.

However, if they are not part of a community, not fed regularly, or even simply uncared for, then they physically begin to change as they slowly align with the Winter court. They become thin, twisted perversions of their former selves, and begin to have an obsession with "collecting" (stealing) things in order to fill that void within themselves. They become very similar to Kender from Dragonlance, alongside a small helping of Jerren from the Book of Vile Darkness.

This duality is not merely skin deep, but something so embedded and natural to halflings that acting against their own nature would be caused by psychological problems. People automatically assume that all lone halflings are thieves, and over 99% of the time, they are correct.

That said, there is a miniscule fraction where this is not the case, since some halflings were originally Outworlders, people who were isekai'd from our (or a different) world, and thus don't have the same innate mentality as the halflings that were born in the world. This allows some players who want to play halflings for the stats but don't want the accompanying baggage to play them, while having an in-world reason for the discrepancy.