I generally author at 60, but you’re right that 30 is standard allowing interpolation to handle the rest.
Unreal imports at 30 by default, but this can be set to 60 when importing an FBX. The most important thing is to import at the rate you authored the animation so you don’t lose any information in the import process.
The reason I author at 60 is because my style includes a lot of manually authored secondary animation and follow through, but this is generally not required for video game-level fidelity unless you’re animating a cutscene with extra details in the motion.