FedEx only requires a signature for the packages when the shipper requests a signature for the package.
Or if FedEx is delivering the packages to a business then FedEx will require someone at the business to sign for the packages when they deliver them.
Most other packages and low value items will not require a signature.
Most packages I order and have shipped to me through FedEx require no signature.
I have had to sign for a laptop computer, I Phone and desktop computer before when it was shipped through FedEx but other items I never had to sign for.
If you do need to sign for a package through FedEx and are not home they will leave a door tag which you can sign and leave attached to your door.
Then the next day when FedEx comes by to attempt redeliver of your package they will leave it someplace out of sight.