If I do need a router it would make sense to eliminate this Cogeco modem that I pay rental on each month and just get my own router as my internet and wifi?
If you get rid of that, you won't have a modem to get your Internet.
Lets talk terminology:
A modem, be it cable, DSL or 4G/LTE cellular wireless, obtains the Internet and passes it on to a router, where, among other functions, a DHCP server hands out IP addresses to device on the LAN (Local Area Network).
A combo unit will have the modem section, a router section and generally, a wireless access point, which also gets the IPs it passes on to wireless devices from the router portion. That's likely what you have.
Most modem/router combo units supplied by ISP's do not provide all the features desired in many instances in the router portion so one would want to turn off the router portion of that combo unit, put the modem into bridge mode so that the modem portion only obtains the Internet and a more feature-rich router can be used outside the combo unit to provide IP's to the LAN, port forwarding (not recommended), VPN (recommended), and other things.