Hi Keith,
just for the rate limiting the WAN connection you can use the configure ports [port_list | port_group]rate-limit egress [no-limit | cir-rate [Kbps | Mbps | Gbps] {max-burst-size burst-size [Kb | Mb]}] command.
To classify traffic and preferring some traffic over the other, you first need to create and configure QoS Profiles (EXOS allows up to 8 of those, 7 if stacking is used), and then use ACLs (or existing CoS or DSCP markings) to assign traffic to the QoS profiles.
Please take a look at the QoS chapter of the EXOS User Guide for detailed information.
If you disregard the flow control commands, the GTAC Knowledge article How to configure Priority Flow Control (https://gtacknowledge.extremenetworks.com/articles/How_To/How-to-configure-Priority-Flow-Control/) gives an example QoS configuration including rate limiting you may be able to use as a reference.
Thanks,
Erik