I know with hardwoods you need 1 1/4 subfloor to go parallel with the joists but pre engineered being alot lighter can you float or even staple or glue this using 5/8 OSB as a subfloor

When you're talking about engineered products always check first with that particular manufacturer on what they suggest as suitable substrates. Their instructions override anything else. If the manufacturer states to follow NWFA guidelines that is a different story. Stapled floors require 3/4" OSB. You can glue or float over 5/8" OSB but you still should cross the joist unless you build it up with underlayment. I don't think I would even glue one over 5/8".

It's paradoxical to read in the instructions to consider the light source when determine direction because technically speaking you rarely have that choice when going over a floor system and floor joist.... slabs or double layered substrates would be OK to consider the light source.