This article explains how to calculate active path in LAG with flooding packet.

Hashing formula for flooding packet is different for each platform.

The hashing algorithm for flooding packet (Broadcast, multicast, unknown-unicast) is not the same as the unicast algorithm.

On EX4200, hash algorithm for flooding packet is the same as known unicast packets that use L2/3/4 header info.
For non-IP traffic, hash is done on src/dst mac addresses so the EX does load-balance non-IP traffic.

On EX8200, hash for known unicast traffic is the same as that of EX4200 described above.

On EX8200, hash for flooding packet is based on ingress port (port where traffic ingress the switch) and ingress VLAN.
What this means is that packets ingressing from 2 different ports, may be load-balanced. Similarly, packets on different VLANs may also be load-balanced.
But, packets on a port and VLAN, with different MAC/IP/protocol ports will use only one member of the LAG.