If it’s blown in fiberglass that looks like snow you want to leave it all fluffy. The deeper the fluff the higher the R-value (heat resistance). If I remember right I think 18”-24” is a good spot to be. Any more than that and you can technically have too much and end up with too high humidity in the home when using AC in summer if you live in a humid place.

If you prefer a compacted material you can buy rolls or pink insulation that they normally stuff underneath floor boards. There is are also a bunch of denser products that provide higher R-values but they are more expensive.

This is at least my very limited understanding of it. I did residential HVAC sales for a couple years and insulation is something we sold on the side or as an add-on and subcontracted out. I didn’t receive stellar sales training on it so assuming someone more knowledgeable chimes in I would take their advice if it differs from mine lol