Yes not ideal, since some tcp ports remain open on the STB, and now they're available "to the outside world".. :/
The WiFi was a no go, I was pretty much ready for that outcome.
The IGMP Snooping is enabled by default from what I could gather, and perhaps it's some configuration that's needed but not available via the webui from the ASUSWRT (not using Merlin).
Don't want to hijack this thread, so I'll stop.. but, my issue is pretty much this https://www.snbforums.com/threads/igmp-snooping-multicast-forwarding-on-ax-routers.58245/
And what's more and I could find out is that on the ISP CPE (ONT+ROUTER) the bridge interface (veip0.2) doesn't have IGMP Proxy enabled..But it's enabled on the default wan interface (veip0.1).
So, for now, I guess I'll keep using it this way as well.
Please report back if you find a solution to enabling the IGMP stuff. I still can't understand if it's a real hardware limitation or just a software problem because this routers uses a new hardware with different config files from before. I'm on VODAFONE but the problem is the same.