Gradle Plugin Confusion

Hello, 
I just want to ask for a little help, because I'm really confused.

I'm creating a IntelliJ IDEA plugin that will provide a Project Wizard. This is closely tied with Gradle, so I somehow figured out this:

intellijPlatform {
    intellijIdea("2026.1.4")
    bundledPlugin("com.intellij.gradle")
    bundledPlugin("com.intellij.java")
    bundledPlugin("org.jetbrains.plugins.gradle")
}
will give me access to GradleNewProjectWizardStep and GradleNewProjectWizardStep classes.
E.g. GradleNewProjectWizardStep has preconfigured methods such as setupGroupIdUI, setupArtifactIdUI, setupJavaSdkUI, etc.

My questions are: Are these official APIs? Does this (bold) plugin have documentation? What is the diference between the two Gradle plugins.

Thank You!