Usually games use UDP, though I guess if the TCP links all get notified of congestion that could effectively ensure there is enough bandwidth available for all the UDP traffic.
If also, the greedy protocols like TCP or QUIC back off on filling up buffers (via an AQM) before a gamer would notice (20ms of jitter/buffering is about right, 60ms is teetering on wrong) gamers and downloaders can co-exist happily on the same link.