Better maybe, but you'll never sleep well if you leave your laptop in your car. In fact, none of us can park in peace because people leave laptops in vehicles.
Only if you shutdown. Otherwise tpm is still in memory and everything is unlocked.
Going off how many people compliance have to chase to restart for updates, a lot of people think sleep is fine
Your average thief has no idea how to get into a system which asleep but screen-locked. FDE means your machine gets wiped and resold, or sold for parts...but your data on the system remains private.