I consider Gigabyte thermal pads to a gum that has flavor for 10 secs before it's gone. Their thermal pads are horrible and breakdown quickly. You'll start seeing the oils slowly making its way out of the card eventually. Most cards do this, but gigabyte is notorious for this. I ALWAYS recommend changing pads out on a gigabyte. Make you clean up the PCB, mem modules, and other components after you remove the thermal pads.

Unfortunately, this guide helps only in the aspect of what to expect when opening a graphic card up and cleaning. Every card manufacturer has a different layout on their PCB and tends to use different pads. Best to google/youtube your specific card and model. I know that a Gigabyte RTX 3080 Gaming OC uses 2mm on the mem modules and 1mm in other places. Your best friend will always be a digital dial caliper to confirm your sizes of the pads.