One of the ip (Shaw Router) maxes out at 30mbps download and the external router at 75mbps.
Both IP addresses will share the 150 mbps. Transfer of
IP1+IP2 < 150 mbps
If I am only connected to IP2, should I be getting 150mbps?
Depends what is happening on IP1, and if you are on wifi: how your wifi is performing, which has little relation to how your internet service is doing.