Best firewall is still a hardware one.
Doubtlessly.
Doubtful.
Unless it specifically states it has outbound protection (then it probably doesn't) it is still vulnerable to non-internet infection. Not to mention if any malware does get past your defences during routine browsing, it is free to connect without hindrance and any associated inbound traffic will sail through too.
So IMHO you still need outbound protection.
Whilst this may well be good enough for very experienced users who basically know how to keep their system clean, so there shouldn't be any non-internet infection. Then it would be an adequate option, but for your average user, they need all the help they can get.