If you specify a limit greater than the maximum throughput of an interface, the system does not rate limit matching traffic. Maximum throughput may be affected by an interface's hardware configuration, which you specify in each device's properties (Devices > Device Management).
https://www.cisco.com/c/en/us/td/docs/security/firepower/640/configuration/guide/fpmc-config- guide-v64/quality_of_service__qos__for_firepower_threat_defense.html

Packet capture is available with the trace option, which provides you with a verdict as to whether the packet is dropped or successful.
https://www.cisco.com/c/en/us/td/docs/security/firepower/650/configuration/guide/fpmc-config- guide- v65/troubleshooting_the_system.html#:~:text=Packet%20capture%20is%20available%20with%2
0the%20trace%20option%2C%20which%20provides%20you%20with%20a%20verdict%20as%2
0to%20whether%20the%20packet%20is%20dropped%20or%20successful

Explanation
https://www.cisco.com/c/en/us/support/docs/security/firepower-management-center/212702-configure-and-verify

When performing packet capture on a Cisco Secure Firewall Threat Defense (FTD) device, ensuring that the allocated memory is sufficient is crucial for capturing all necessary traffic during a specified capture session. If users experience issues accessing a server and the engineer suspects not all traffic was collected, it indicates that the current memory allocation might not be enough to store the entire capture data for the 15-minute session.
Steps:
* Check the current memory allocation for packet captures on the FTD device.
* Increase the memory allocation if it is insufficient to handle the volume of traffic expected during the capture session.
This ensures that all relevant traffic is captured and can be analyzed to diagnose and resolve the network issue.
References: Cisco Secure Firewall Threat Defense Configuration Guide, Chapter on Packet Capture.

With tap mode, the FTD is deployed inline, but the network traffic flow is undisturbed. Instead, the FTD makes a copy of each packet so that it can analyze the packets. Note that rules of these types do generate intrusion events when they are triggered, and the table view of intrusion events indicates that the triggering packets would have dropped in an inline deployment. There are benefits to using tap mode with FTDs that are deployed inline.