Kinda but not really, they're both made from glass fibres, but are a very different product that serves a very different purpose. Fibreglass typically comes in a flat cloth, and is used with resin to create something structural.
I worked on a few buildings where they used straw balls lenght wise. They had meter thick walls and it's very efficient. One of them only had a tiny wood stove
just an air gap is not that good as convection will move the air around decreasing its effectiveness. Most insulation is just a way to try to keep the air in place while the air is doing the actual insulation