Bevendre

A changeling’s fire developed as a defense mechanism to blind and escape predators and attackers, before they developed the capacity for natural shapeshifting, but after their hide became as chitinous and hard as it is.

A changeling’s sense of touch is somewhat diluted because of their hide, but not by much.  In their base form, a changeling’s chitin is hard and warm to the touch, both less yielding and less furry than a pony’s hide.

Papillon respects Chrysalis’s status as a Queen, but is extremely dissatisfied with her practices and actions.  Papi is a pacifist, and will not initiate an attack on Chrysalis, though she will defend her subjects and offspring until her last breath.

Papi would not overthrow Chrysalis for the betterment of all changelings, but does encourage Chrysalis’s subjects to choose their ruler for themselves.

If Chrysalis came barging in on a power trip then she would be struck down and made to kneel before Papillon.  There is no single ruler of the changelings, but Queens of individual hives, and Chrysalis would be expected to pay homage to Papi within her own hive.  

If Chrysalis came to Papillon for help, the Papi would help her, but not without reprimanding her for her brash actions, and violation of the changeling way.

At the head of the hive is the Queen, for obvious reasons.
A Queen will generally choose either one or several converted drones to serve as a sort of cabinet and manage hive affairs when they build up.
Beneath these few are the converted drones as a whole, each bringing something unique to the hive.  
The natural born drones are those whose eggs are carried by converted drones.  These often bear a physical resemblance to their parents, having average horns and wings, though their coloration is generally muted or akin to those that attacked Canterlot.
Warriors are below the drones and make up the bulk of a hive’s defenses.  Born directly from the Queen, they are generally less intelligent than their drone counterparts, but taller and stronger, as well as bearing thicker hide, and added chitinous plating along the head, back and shoulders.  Goliaths stand as paragons among Warriors, renowned for their massive size and strength, despite their lesser intelligence.
On the bottom of the general social hierarchy are the Workers.  Like the Warriors, Workers are born directly from the Queen, but in much larger numbers and without wings.  Possessing of clever minds and swift hooves, Workers remain almost solely within the hive, tending to the tunnels and rooms within.  Though they are often very intelligent, they are also very dependent on the other changelings for sustenance and blindly loyal to their mother and Queen.

Many do enjoy swimming or relaxing in bodies of water, but that is more for relaxation than bathing.

Because their hide is chitinous and rather hard it is not easy for dirt or grime to stick, nor can many parasites penetrate it.  The fire a changeling produces when it shifts shape is not only not merely for aesthetics, but burns just hot enough to purge a changeling of most issues as far as cleanliness goes.

Changelings are creatures made to adapt to new situations and environments, so many would most likely at least try to build cities above ground.  Granted, these cities would most likely reflect their subterranean hives and could even be comparable to termite mounds in their size and complexity.

There would likely be some purists who preferred to retain the old ways however.  There always are.

A physical show of love and affection between love eating cuddlebugs?  No, changelings do not like to cuddle, they love it.

Good Will is still within the hive and will act as a sort of emissary between the hive and Equestria in the future.  As he has chronicled the hive’s history thus far and does not slander Papillon or her subjects with prejudices his work is seen as invaluable to showing that changelings can live peaceably with ponies.

He is under Papillon’s protection within the hive, and it shall remain so in the future.

This arose out of ask-goodwill approaching me directly early on with such a suggestion.

It is possible that there would be ponies who are naturally aware of changeling tricks and practices, and who would resist consumption on the emotional level, but perhaps not the physical.

Papi will only convert a pony if they are willing to join under their own volition upon discovering the hive, and if that is not an option and they prove no great threat, then their memories are altered and they are escorted out of the hive.

Even if a pony can resist a changeling’s natural wiles, there are few who can resist upper level hypnotic magic.