Isn't it heavy and slow though? At least that's what I hear. I use android studio in a beefy macbook pro from time to time and it's slow as hell.
Jetbrains uses Swing not JavaFX from my knowledge. And yes, the performance can get slow for a Java app on the scale of Android studio but that shouldn't be of concern to a beginner.
> as the have the JRE installed.
Does this come packed with most platforms (Mac, Linux, Windows)?
No, but nothing else does either - you'll need to ship runtime environment in any case. And packing JRE is more cross-platform tested than most other solutions.