Found in GameData/WhirligigWorld/Settings.cfg, the settings file for WhirligigWorld contains a few customizable gameplay options. Changing the settings is simple, but in case you mess it up, I'd recommend that you back up the default settings.cfg file and change the filetype to settings.txt.

Homeworld Swap

    //pick either Mesbin or Kerbmun.
//default is Mesbin.
//I highly recommend playing with Mesbin, it's a really fun challenge to play in this wacky homeworld.
//However, if you REALLY want a more down-to-earth gameplay, let's rewrite history so that the colonists DID land on Kerbmun with a certain degree of success.
//When set to Kerbmun, some of the science definitions may still refer to Mesbin as a homeworld, and you will revert to the stock tech tree.

//---IF YOU'RE USING INTERSTELLAR CONSORTIUM AND WANT TO SWITCH TO KERBMUN---
//You will also have to go in the IC settings add homePlanet = Kerbmun.
//By default the homePlanet = Kerbin setting is commented out. If it isn't, change the existing homePlanet = setting to target Kerbmun.
//And make sure you're using WW/Kaywell as the home star, both for Kerbmun and for Mesbin based space programs.

The homeworld swap feature, pioneered by my older mod Alien Space Programs, allows the user to change the location of the Kerbal Space Center to either Mesbin or Kerbmun.

I highly recommend playing on Mesbin for a while before playing on Kerbmun--one of the major points of Whirligig World is the uniquely challenging homeworld. However, if you have decided you'd rather experience the planet pack as a more conventional solar system replacement with a Kerbin-like homeworld, simply changing the value "Homeworld = Mesbin" to "Homeworld = Kerbmun" will allow you to start on Kerbmun.

Mesbin's surface may be a drab place, but remember that underneath all that rock, in lava tubes and caves, is a home with a rich, centuries old cultural history. Kerbmun may be better for Kerbals as a species, but Mesbin is still the home to your astronauts, and they will probably want to return to their families and friends just as much as if they had launched from Kerbin.

Kerbmun Space Program isn't quite as polished as Whirligig World proper, but it doesn't experience the SOI Kraken bug that plagues Mesbin Space Programs. Descriptions, Science Definitions, and Science Multipliers have been changed to account for the new homeworld. The backstory here is an alternate history. What if the U.S.C. Manifest Destiny hadn't crashed into Mesbin, but had instead successfully crashed into Kerbmun?

Now that Whirligig World has support for Kopernicus' Unique Body Identifiers, it is possible to change this setting without breaking your save files. But to be safe, it's probably best to backup any save files you care about before attempting this.

Unofficial Mesbin to Kerbmun Infrastructure Challenge

So you want to get a taste of life on Mesbin without staying down on that horrible spinning pancake forever? Want a breath of fresh (hypoxic) air? Well here's the unofficial colonization challenge. Fulfill these requirements and you have my permission to continue your save file on Kerbmun, no judgement. ;)

• Mesbin Orbital Infrastructure: You must have set up the mining/refining/refueling infrastructure to launch passengers into Mesbin orbit and return them safely to Mesbin.
• Mesbin Trans-Orbital Infrastructure: You must have set up the mining/refining/refueling infrastructure to move passengers between Low Mesbin Orbit and Troymin and/or Kerbmun.
• Kerbmun Infrastructure: You must have set up the mining/refining/refueling infrastructure to land passengers at a Kerbmun surface base which can support kerbals, and then refuel the vehicle, and return to orbit and repeat.
• Mesbin/Kerbmun Freight Lines: You must have set up the infrastructure and have the spacecrafts capable of sending cargo, be it new base parts or new vehicles, from Mesbin to Kerbmun.

Once all of this is completed, you can go into the settings.cfg file and move the homeworld from Mesbin to Kerbmun. This should be a seamless transition.

Mesbin Exosphere

    //---------YOU MUST SET THIS TO TRUE TO START CAREER MODE ON MESBIN----------
//or else you will not be able to complete the "First Spaceflight" contract.

//Pick either True or False.
//default is True.
//When set to False, the atmosphere will be limited to the atmosphere over the North Polar Basin.
//When set to True, the atmosphere will go up to about 1980 meters above Mesbin Space Center, or 970,000 meters above the datum/sealevel.
//...However, almost all of it will be vacuum, hence "exosphere."
//Once you've completed the "First Spaceflight" contract, you can set this to False before your next restart, or at any other time.
//Just be sure to turn it back on when you start your next career mode!

Kaywell Barycenter

    //Pick either True or False.
//default is False.
//When set to False, Kaywell will have 1.7 Solar Masses and will be the center of the system.
//When set to True, Kaywell will have the realistic 1.17 Solar Masses and will be in a binary orbit with Limnel.
//Note that when Principia is installed, Kaywell will have the realistic 1.17 Solar Masses and will be at the center of the system.
//YOU MUST SET THIS TO FALSE TO PLAY WITH PRINCIPIA.

Realistic Asteroids

    //Pick either True or False.
//default is True.
//When set to False, the densities of the new asteroid types will be divided by 100 to bring them more in line with stock asteroids,
//and the sizes of asteroids will be reset to the stock scales
//Does not apply to Diddmun.

This setting enables or disables realistic asteroid densities as discussed in the Asteroids wiki page.

Scaled Clouds

    //Pick either True or False
//Default is True
//When set to True, Derbin and Imterril will have clouds painted onto their scaledspace maps, disappearing within the atmosphere.
//When set to False, the default blue ocean texture is used for Imterril and the default planet map is used for Derbin.
//This option is automatically disabled if Environmental Visual Enhancements is installed.

KronometerMode

//Pick MesbinClassic, MesbinKerbin, MesbinEarth, or Kerbmun.
//Default is MesbinKerbin.
//Requires the Kronometer plugin to be installed to do anything.
//This setting will determine which clock system is used.
//MesbinClassic: 1 day is equivalent to 1 hour, with 40 40-second long moments making up each day. 1.063125 seconds per second.
//MesbinKerbin: 1 Fortnight is split up into 6 hours, with 60 minutes per hour and 60 seconds per minute. 1.1025 seconds per second.
//MesbinEarth: 50 days are split up into 24 hours, with 60 minutes per hour, 60 seconds per minute. 0.984375 seconds per second.
//Kerbmun: 1 day is equal to the Kerbmun day, split into 30 hours, with 60 minutes per hour, 60 seconds per minute. 1.0093714 seconds per second.

This setting allows you to choose which clock you use with the Kronometer plugin. It does nothing when Kronometer is not installed. More information about the different clock modes can be found here.