I've used my own router on a T3200M without putting it into bridge mode. Just have to make sure the subnet on your personal router is not 192.168.1.x.
I had the problem of the second router assigning IP addresses to devices connected to the T3200M. Bridging port 1 seems to have stopped this issue.
I actually never had any issues gaming with double NAT. Then again it may also depend on the games you play.
You can pull the SFP out and put it into a media converter or an SFP (non +) capable switch. Not all devices support these SFP ONTs though and some don't have decent cooling for them and tend to cause the SFP module to overheat and restart.
If you have an ONT you can remove the T3200M completely and connect directly you just need to make sure your router supports IGMP Proxy with quickleave off.
Telus isn't doing anything special with all this and that's a good thing it's really easy to use your own stuff not that'd they support it.
You can add a switch between the ONT and your routers, or bridge the T3200M to a second router. The ONT follows the same process Telus has always offered: a single path to your router/gateway.