Car seat decisions

I thought with this pregnancy I was being smart and bought a 3 in 1 car seat from 5 lbs to 80 thinking this was smart idea only have to buy one car seat. But now I'm second guessing myself . Alot of people I notice use the carrier car seats at first which also comes in handy when out and about shopping etc etc . Other then a carrier that I plan on getting and just having my daughter in that do I need a carrier car seat also ? Side note will they let you leave the hospital if she's not in one of those carrier car seats ? I have to carry her to the car then strap her in . Sorry in advance I'm thinking maybe I'm thinking to much on this lol