Two separated RBs (LoadBalancer and PPPoE-Server) how to dst-nat

Hello everyone,
I have 2 RBs, one as pcc-balancer and other as pppoe-server, they are bound by a / 30 network, and I have a nat-masquerade rule in pcc-balancer and a route to the address range of the pppoe clients, my question is :
How to do dst-nat ports of the first RB (LoadBalancer) for the client on the second RB (pppoe-server).
Dst-nat in the first RB directly to the IP address of the client, or dst-nat to the end of the /30, and another dst-nat in the second RB to the client address?