If they are converted by your platform as an image, then they will look exactly as defined by the image. For example, most emojis on the forums here use Twitter’s twemoji set to keep it consistent.
If I understand what you are saying, you want to use emojis in your code editor. The emojis in your code editor will almost always be the system default one, not the more detailed SVG versions that you may see when Wordpress automatically converts them when you are previewing them. That your system default emojis from the code editor get turned into more detailed versions is a Wordpress feature.
You can expect that if they are converted to an image by your platform, they will appear exactly as you have defined in the image. A good example would be the use of Twitter’s emoji set for most emojis on the forums here so that everything is consistent.
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