G3100 has a more robust build-in firewall than G1100. G1100 will fall out of support soon as it is two generations behind. Currently, no feature upgrades will be provided for G1100. When it reaches end of support/end of life, no critical security patches will be provided and thus continued use of G1100 will be a security risk.
Regarding UPnP, it is insecure. According to Kayas et al. on IEEE, "a limitation in using the UPnP protocol to support [IoT] deployments is that it was not designed to address security as a first-order concern." https://ieeexplore.ieee.org/abstract/document/9284885/authors#authors For security considerations, UPnP should be disabled on routers regardless whether it is a G3100 or a G1100.
To allow game consoles to be accessed from the Internet, you can substitute UPnP with Port Forwarding (which is not much better in security, if not worse) or wait IPv6 deployments in your region. Using IPv6 would allow each device on your network to have a public routable IP (in other words, all are exposed to the public Internet), which introduces a whole new set of security issues that all devices need to have robust host-based firewall, if the network firewall is not next-gen rated.
