Every official playable race in D & D is, to my knowledge, either medium or small. Even for creatures that are supposed to be big (meaning that the "monster" versions of such creatures are large, like centaurs, minotaurs, etc.), the official playable racial versions of these creatures are considered medium, even if they are against the refreshed upper limit from medium.
There are no official playable races that are tiny. I read this question about problems with homebrew pixie racing and used equipment designed for at least small creatures and more. This made me think about how feasible a small playable race is at all. Before trying to assemble Tiny myself, I wanted to find out about possible issues before I let myself in, similar to this question.
Some of the issues highlighted in this other question (about pixies) are the above-mentioned issue with equipment size, but also things like (as mentioned at the end of the accepted answer) getting into a creature's mouth and entering it, causing damage inside (although this was related to the enlargement of an item in a creature, but still …)
On the other hand, it is already possible to get a Tiny PC from RAW (albeit temporarily) by casting zoom in / out on a small creature (ie gnome, halfling, goblin, etc.) to make it tiny. This implies that there is nothing a homebrew tiny race could do that a halfling wizard could not do.
Which equilibrium issues (whether for the benefit or the detriment of the player of the Tiny PC) would result from a PC, which is Tiny by default. That should keep me busy, should I try to bring home a Tiny race?
In other words, assuming that a small race is definitely balanced, because you can downsize a small race zoom in / outIs that a correct assumption, or am I missing something?
For example, suppose I want to brew my own pixie race, which will be Tiny. I'm not interested in existing homebrew tiny races, including pixies, because the focus of this question is on the impact of the fact that it's Tiny, not that it's a pixie. In other words, this question is not "how to brew a pixie yourself"; rather "if I did it, what to look for".
I also do not think that this is a duplicate of How do I deal with a small player in 5e? Is, since this question asks for rules that already exist for a small character, while I ask for unforeseen effects that result from the permission. The answers are useful, but they do not quite answer my question, which I think is different.