One of my favourite critters is the Draco Volans, and I'm working on a racial splat for a Humanoid-sized player race based on this little reptile for a D&D 5e campaign.

Using the Aarakocra stat splat as a starting point, I downgraded 'Flight' to 'Glide' and adding a climbing speed. I'm a little concerned that the downgrade would make this race underpowered and that the wording for the 'Glide' is too cumbersome.

And without further ado, the proposed racial traits are:

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  Ability score increase: +2 DEX, +1 WIS


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  Size:: Medium


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  Age: Yes


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  Languages: Draconic & Common


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  Speed: 25' walking; 25' climbing.


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  Climbing claws: Grants climbing speed; Natural weapon for 1D4 + Damage bonus (finesse)


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  Glide: You can glide for short periods of time. You have a fly speed of 60', but cannot gain altitude with this trait. While gliding, you descend at a minimum rate of 5' vertically for every 15' travelled horizontally. If you are still in the air at the end of this movement, you fall. You cannot use this trait if you are wearing medium or heavy armour.

Is this racial template balanced with respect to the official published races?

This race is comparable in power to the Simic Hybrid race published in Guildmaster's Guide to Ravnica; probably underpowered

In some respects, I'm inclined to argue that it's a strictly weaker version of the Simic Hybrid, with caveats.

The main feature of the Simic Hybrid is that twice, once at level 1 and again at level 5, the hybrid is allowed to choose specific features to "augment" themselves with. There are 6 features in total that the hybrid is allowed to choose two of, but two of those choices are extremely similar to what you've listed here:

Manta Glide You have ray-like fins that you can use as wings 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.
Nimble Climber You have a climbing speed equal to your walking speed.

[...]

—Simic Hybrid, Guildmaster's Guide to Ravnica, pg. 20

So approximately, your race is equivalent to choosing Simic Hybrid but being locked into those two choices; but also gaining a [Finesse] Natural Weapon you may use instead of the Darkvision that Simic Hybrids get by default.

Even just in the context of the specific "slow fall" feature that your race gives, what you're offering is a little bit underpowered, given that the Manta Glide feature negates up to 100 feet of fall damage, whereas your feature only negates up to 60 feet; although your feature also allows for more horizontal movement per vertical movement.

The main potential benefit of your race is that it's extremely well suited for Rangers, Druids, and Monks, who otherwise would not be able to optimize both Dexterity AND Wisdom as a Simic Hybrid.

But even so, you could probably get away with buffing one or more of the features provided by this race. Maybe bump the walking/climbing speeds up to 30' and give the glide ability a longer range. Then you'll at least be on par with an official race.

Using the Detect Balance: a 5e Homebrew Race Guide
you end up at 19-21 depending on how you value the -5ft fly speed and the combination of WIS and DEX which leaves you around the power level of a Dragonborn (21) or a dwarf without a subrace (20). This is on the weak side, but balanced.