If you don't map ports to computers behind the nat router you'll be safe from outside connections. However, a software firewall such as zonealarum can be usefull for stopping outgoing connections such ...

I've been considering securing my home network for a while and I'm wondering if a router's NAT firewall is good enough to protect oneself or whether I should have a dedicated physical firewall ...

The first step to correctly answering whether you can change NAT settings without logging into the router is knowing exactly what NAT is and how it works. Then can you figure out how to change NAT ...