@B700
Hello, Archer AX1800 supports QoS only, it doesn't support bandwidth management for the Guest network. Here's how to use QoS on your device (Case 1), you can confirm if it helps with your requirement to limit the bandwidth or speed usage by the devices connected to the Guest Network.
The good news is we do have a plan to add the Bandwidth management for the networks, and AX73/AX4400 already support that, you can visit this thread for more details:
Speed Limit on Wi-Fi Routers
However, we don't have an answer as of now whether AX1800 or other models will support it as well, or when that will be, the only suggestion would be to pay attention to the new firmware release for your model, you can find the updated information in the release notes. We will also update the above thread to inform you if there are other models that support Bandwidth Control, you can subscribe to it to get advanced notice.