There are two variations of changeling actually. In both of them it is 4 ft to 8 ft and the size of changeling is defined as 'Medium'.
Size. In their natural forms, changelings average between 5 and 6 feet in height, with a slender build. Your size is Medium.
The only other limitation is you cannot change your size category: as a Medium creature you cannot become a Large or Small creature - you can become a dwarf, you cannot become a gnome. Well, you can but you'll be much bigger. It's just appearance that changes not your race.
Lifespan. Changelings reach maturity slightly faster than humans and live as long as humans do, typically about 100 years.
5e Changelings have basically no drawbacks. Can turn into any medium humanoid creature, no saving throw concentration on holding a disguise if you take damage, and the disguise is considered perfect unless you do something REALLY out of character.
A changeling can't make the wings at all. If they had wings, like from a class feature or something, then they could look like an Aaracokra with wings because they will have those limbs at that point.
If the changeling has lost a limb, the limb is missing in every form they take. If they haven't lost a limb, every form they take has all the limbs the changeling normally has.
As an action, you can change your appearance and your voice. You determine the specifics of the changes, including your coloration, hair length, and sex. You can also adjust your height and weight, but not so much that your size changes.
Within this description there are variants of changelings that show subtle differences. Some have opalescence in their skin (as if it contains various colors instead of just being white) and their eyes can be completely black.
Are they biologically asexual and just choose their current sex with shapeshifting? Yes. What's been stated in the past is that changelings set their sex with shapeshifting.
A changeling can alter his or her gender (and reproductive abilities) as part of using the race's minor shapechange ability. Two changeling parents breed a changeling child. A changeling and a humanoid can mate to produce an offspring with the child having a 50% chance to be of either race.
As for being tattooed, changelings can definitely be tattooed, and they can just as easily erase the tattoo with a moment's thought.
They also have more physical differences among them: some possess longer, more jagged horns, and others no longer have horns at all. Others still no longer have tails. Some also have a trio of gemstone-like objects in their chests. Like Queen Chrysalis, the changelings were designed by Rebecca Dart.
Changelings have an interesting relationship with gender as a concept, which is probably part of the reason a lot of the art doesn't find it necessary to distinguish the males with facial hair. As they're changelings though, they can have any kind of hair they want.
Changeling Traits
Age: Changelings reach adulthood at the age of 16. Their fey heritage allows them to live much longer than humans, up to 200 years.
"A human child might be taken due to many factors: to act as a servant, the love of a human child, or malice. Most often it was thought that fairies exchanged the children.
Changelings have red blood like a majority of the other races. Bleeding around others may alert many that the Changeling is not of the same race (should the blood color vary). For this reason, a Changeling will usually choose to take the form of a race with red blood.
Changelings are typically born with female anatomy, but some prefer to maintain male primary and secondary sex characteristics once in control of this ability.
Changelings born from two changeling parents are born in their natural form: pale, slender, with colorless eyes and white hair.
Obviously, a changeling's appearance can change at any moment, but they do have a true form. Their true skin is usually grey or pale white, and their facial features are blank slates to an unnerving degree. They're typically thin and gaunt, and their hair is usually silvery with an occasional green or pink tint.
Most often, the mother begins to carry twins, and one of the twins is a changeling. There are extremely rare cases of being born alone, or as part of triplets. In the rarest of cases, the other twin is a hag.
Most changelings don't know they're changelings.
Though they may always feel somewhat different or removed from human life, most changelings are too young to understand who they truly are.
The true form of a changeling is a bit paler than a typical human with slightly elongated limbs. Their eyes are colorless and ringed by black as pictured in the artwork above by Julia Zhuravleva. They have no body hair, but the hair on their head can be platinum, white, or silver.
Changelings are largely equine in appearance but possess insect-like characteristics. Originally, they had black carapace-like coats, webbed manes and tails, blue reflection-less eyes (unlike their queen's), fangs, bent horns, jagged ears, insect-like wings, and holes in their legs.