When comparing the dragonborns with the other races of the Player's Handbook, it is pretty clear they are a bit underpowered. A quick search in google shows many people also think so.
Besides their damage resistance, dragonborns only get their breath weapon. Dwarves get five traits along their resistance to poison (their only let down being -5 feet of movement) while tieflings get two traits along their resistance to fire, with a free cantrip and 2 spells/1 day with some levels being one of the traits.
The problem is that the breath weapon doesn't make up their lack of traits. It is indeed a very good damage AOE in lower levels, but it scales poorly, takes an action and it can be used only once per rests. Most races have traits that are much more useful independent of level/scaling.
So I created this version of the dragonborn using other racial traits, loosely based on what a humanoid dragonborn version of Spyro the Dragon would be. I plan to present this as a player option in an upcoming campaign where I will be the DM. Is this somehow unbalanced when compared to the other races of the PHB?
Ability Score Increase. Your Charisma score increases by 2, and two other ability scores of your choice increase by 1.
Size. Dragonborn are taller and heavier than humans, standing well over 6 feet tall and averaging almost 250 pounds. Your size is Medium.
Speed. Your base walking speed is 30 feet.
Breath Weapon. You can use an action** to exhale destructive energy. When you use your breath weapon, each creature in a 15-foot cone must make a Dexterity saving throw. The DC for this saving throw equals 8 + your Constitution modifier + your proficiency bonus. A creature takes 2d6 fire damage on a failed save, and half as much damage on a successful one. The damage increases to 3d6 at 6th level, 4d6 at 11th level, and 5d6 at 16th level. After you use your breath weapon, you can’t use it again until you complete a short or long rest.
Draconic Swimming Training. You have a swimming speed of 30 feet and you can hold your breath indefinitely while underwater and you’re not incapacitated.
Horns. Your horns are natural melee weapons, which you can use to make unarmed strikes. If you hit with them, you deal piercing damage equal to 1d6 + your Strength modifier, instead of the bludgeoning damage normal for an unarmed strike.
Goring Rush. Immediately after you use the Dash action on your turn and move at least 20 feet, you can make one melee attack with your horns as a bonus action.
Glider Wings. You have small wings that you can use to slow your fall or allow you to glide. When you fall and aren't incapacitated, you can subtract up to 100 feet from the fall when calculating falling damage, and you can move up to 2 feet horizontally for every 1 foot you descend.
Languages. You can speak, read, and write Common and Draconic.
** Posted originally as bonus action, just to clarify.