This is a really great question!!!
I cheated a little in that my multitool has a removeable flint attachement that I can start fires with. With that and a some paracord and water purification…I figure I can “McGyver” everything else (traps, shelter, slings, etc).
I have several bags at the house, one for each family member that’s about the size of a school backpack/daypack and has the essentials (actually mine and my son’s are our Scout Essentials packs)……I have a bag in the back of my truck that I’d consider a “get home bag” but it’s a medium sized pack, weighs almost 30lbs and is designed to get me through at least 72hrs of an emergency should I need to trek home from someplace, or get stuck in a snowstorm or get lost/stuck out in the back country somewhere (I would probably take it instead of my essentials pack in an emergency where we had to leave home).
We also have a family first aid bag for the house that can be thrown over the shoulder and taken quickly and I have a pretty serious first aid bag in the back of my truck (in addition to my bag) in case I come up on an accident and can render assistance.
Having said all of that the three most important things that you need to take with you don’t go in your bag…and that’s a brain, common sense, and some basic emergency knowledge (first aid, navigation, shelter building, etc). If I had to add a fourth, I’d say confidence…confidence that you’ll make it through whatever event you’re experiencing.