I've noticed that jME tutorials mostly use y-up for world space.
Do you mean to say OpenGL is y-up in the sense of identity?
OpenGL is a Y-up system. An so is LWJGL (the underlying gears of jME). It just seems natural to keep the same standard up the hierarchy.
Yes, while modeling community uses Z-up
Thanks for the info … as you might can tell I'm new to the gaming community.