Good post! I guess the 1st thing I think about is how big were the bags? I realize we don't know that, but it would make a huge difference as to what the bags could have contained. For example, if they are small (like grocery sacks) maybe there's a bath towel and a sponge in a bag, maybe her shoes in a bag along with another piece of clothing? Maybe some washcloths, hand towels? Maybe FD's and MT's clothing, shoes, etc were in some of the bags? Maybe some cleaning supplies, rags, bleach bottles? Maybe some paper towels used for clean up? Maybe things used in the attack/murder, such as murder weapon. Maybe some hazmat-type disposable clothing? Maybe some things that happened to be in her garage that MT/FD could see had some blood splatter on them? If they are big lawn/trash bags, maybe bucket, maybe blankets? Possibly a tarp or rug that was used to conceal the body? Maybe seat covers out of vehicle that may have had blood stains or possible DNA on them? Maybe floor mats from vehicle(s)?
Just a few things that come to mind when thinking about the number of bags and what could be in them. This is all JMO/thoughts/guesses.