Difference between Write Normals and Smooth Groups option in export .obj? Hi its just a simple question, whats the difference between those two? its sound like they do something similar, but in which case should i use one over the other?
Also if i can get a good explanation of those two would be great.

(i ask this looking to make some assets from high to lowpoly and baking in xnormal, so im using auto-smooth sharp edges, etc)

Thanks!
Write Normals does what it says - it write actual normals (face corner ones, i.e. one normal per face and per vertex). This is the most powerful and precise option, since it not only allows support of sharp edges and smooth faces, but also advanced low-poly tricks used in games and architecture, like 'rounded' edges etc.

Smooth Groups are a simplified version to store some non-uniform shading, it defines groups of faces that form a smooth surface. Meaning, edges between faces of a same group are smooth, while edges between faces of different groups are sharp.

Which one to use is mostly a matter of “what is supported by target application(s)”, though I would recommend to try normals first, since they allow more possibilities.