Estimate data used by online gaming.
Online gaming is counter-intuitive: the gameplay itself is light, typically 40-100 MB an hour because only positions and inputs cross the network, while the downloads are enormous. A single modern title is 50-150 GB and patches routinely run 10-30 GB. That is why the download share is almost always above 90 percent and why capped connections are strained by installing games rather than by playing them.
Gameplay plus download traffic
Gameplay GB = MB per hour x weekly hours x 4.35 / 1024; download GB = downloads x average size; total = gameplay + downloads
Most competitive shooters and battle royales run 40-80 MB an hour. MMOs are similar. The exceptions are cloud gaming services, which stream video and consume 4-20 GB an hour depending on resolution.
Somewhat. Turning off automatic updates for games you no longer play stops the largest avoidable share, and some launchers offer a lower-bandwidth or off-peak download schedule. The patch itself cannot be made smaller.
Low latency. Because the per-hour data rate is small, a 25 Mbps connection with 20 ms ping outperforms a 500 Mbps connection with 90 ms ping for competitive play. Speed only matters for how fast the game downloads.