What are the common Best Practices for configuring QoS over a route-based VPN?

What are the common Best Practices for configuring QoS over a route-based VPN?

A.
Ensure the VTI is unnumbered.

B.
Ensure the VTI is numbered.

C.
QoS is not supported.

D.
IKE traffic must have a minimum Guarantee of 50% of the external interface throughput.