Races

Halflings

Halflings receive a +3 bonus to-hit with slings and bows, as per the Monster Manual.1) The PHB says, under the halfling section, to reference the MM for more halfling info. Furthermore, the Elf entry in the MM lists their +1 with bows and swords in the same spot as the sling and bow bonus is listed for halflings. Finally, halflings are already strength and level capped. This is a fine benefit to give them.

Elves

Elves can move, shoot, and move again, as per the MM. More on this in Combat.

Half-elves

Half-elves can wear items made for humans or elves, unless the item in question specifically lists half-elves as being in a different category. 2) We could get into average heights and weights for each race and make charts and do math but that’s more complex than needed.