Vpn to a firewall behind a peplink

we have a fortinet firewall thats sitting behind a peplink balance 50.
is there a way to VPN into that FW directly? what set of rules need to be set on the peplink to allow this ?

If the VPN establishes on a single WAN only, I would recommend the following steps:

  1. Check the preferred WAN under Network> Misc. Settings> Service Passthrough Support> IPsec NAT-T “Route IPsec Site-to-Site VPN”.
  2. Set up port forwarding rules or configure a NAT Map to the Fortinet
  3. Configure inbound firewall rules to allow VPN traffic if the default rule is set to “deny”.

Sorry for replying to an old forum post. I am currently doing this kind of setup in the office.
I understand the answers for no. 1 and 2.
For no. 3, If the default firewall rule is set to allow, do I still need to create separate rules for any other services such as SSLVPN service, email service?