> do I need to order another aftermarket router for security reasons? Is there a security risk using the Shaw system?
Routers do "NAT" (Network Address Translation). Any traffic originating on any of the computers on your LAN have their "private" IP-address "translated" to the "public" IP-address assigned to the "WAN" side of the router. That's easy to do. Compare this to anyone inside your home using one of the landline-connected hand-sets to originate a call -- the Caller-ID that the recipient sees is that of your single telephone-number, not which handset placed the call.
However, the other half of NAT is to keep track of which of your LAN computers sent something, and then to allow the response to be routed only to the computer on your LAN that is expecting the response. Note that this NAT process acts as a "firewall" -- it will "drop" all incoming traffic that it cannot map back to one computer on your LAN. Very secure! Compare to somebody telephoning your number, and asking to speak to a person who does not live in your house -- you just terminate the call.
While your Shaw router was "bridged", its "firewall" functionality was disabled -- all unsolicited incoming traffic went through to your own router, but your own router also is doing NAT -- and your router will be the device that "drops" such traffic.
If you just had one Windows/Mac computer directly connected to the "bridged" Shaw router, the Windows (or Mac) Firewall would be blocking all that unsolicited traffic. Of course, if a computer-virus disables the firewall software, your compromised computer becomes even more vulnerable.
So, the firewalling done by one of your devices (Shaw router, your router, your computer) gives you protection from incoming unsolicited traffic.
> is it worth upgrading to the fiber plan?
It depends. How often do you connect to servers on the Internet that can deliver a steady stream of 600 Mbps traffic to your computer? Compare to watching 3 AM traffic on a highway -- each car/truck is travelling at the posted speed limit, as it would in the daytime, but the gaps between vehicles are much larger than in the daytime.
How often do you have 6 computers on your LAN, each interacting with different servers, each sending at 100 Mbps? In that case, the 6 streams, each at 100 Mbps, will "fill" your router's connection from the Internet, namely 600 Mbps, in the aggregate. A six-lane highway can carry 6 vehicles, each travelling at 100 Km/hr. But, at 3 AM, not all those 6 lanes will be full.
