The concept is right mrfuji3, but I wouldn't touch things like AC and DC. Bounded accuracy is stable and amazing, but also delicate. PB to damage on the other hand is interesting for orcs, but feels more like a cultural thing rather than physical for elves. I'd go with a double range on ranged weapons to stress their long sight. The advantage on identifying spells that as been suggested before is even cooler because it's usable by more classes.
On top of that, IIRC, small creatures already have disadvantage against bigger creatures.
There are one thousands way to improve races and make them more unique. We can list them for months without getting short of new ideas. The point is that a feature will always be more interesting than a number.
Sure, my specific examples were just that: examples. What's important is that the racial differences are mechanically impactful, (mostly) unique, and define core aspects of races.
You're only partly right about small creatures. If I'm not mistaken, the only differences between Medium and Small creatures is that the latter have disadvantage when using Heavy (i.e., Two-Handed) weapons and cannot grapple/shove Large creatures. With normal weapons, a Halfling is mechanically as effective as a Medium creature. And small races can grapple & shove medium creatures at no penalty (I *strongly* disagree with this rule). So there are certain characters that you can't do with small races (two-handed barbarian titan-grappler), but most character concepts are relatively unaffected.
Afaik, small races have the *same* carrying capacity as larger races. It's only Tiny creatures that have their carrying capacity halved.
In sum: imo 5e messed up by removing most size differences and thus making races more homogenous = boring.
