DrayOS routers generally support up to 500Mbps NAT performance, if higher throughput is required, we usually recommend to enable Hardware acceleration.

However, some of the features are not possible to be executed together with Hardware acceleration such as QoS, Bandwidth Limit and Data flow monitor.

this is because the router needs to check packets one by one when these functions are enabled, therefore the packets can't be passed through hardware acceleration directly or the function will fail.

It means when these functions are enabled, the router will execute them in higher priority than Hardware acceleration. Speaking of this, we can imagine if users report the hardware acceleration doesn't work properly, it may due to these functions being enabled.

There are two functions, WAN budget and Traffic graph which have lower priority than hardware acceleration, you can see the notes or the warning message asking you to "disable the function" when you enable Hardware acceleration.

To find more info, you can check the article here:  https://www.draytek.com/support/knowledge-base/5308