IP Passthrough

We have our Pepwave MAX BR1 Mini LTE LAN port connected to our Meraki MX67 (2nd WAN interface). We are not using the BR1’s WAN interface. The WAN is not using bridge (IP Passthrough) mode. So when our primary ISP fails on the Meraki’s primary WAN, the secondary WAN interface (the BR1) successfully provides the failover to its cellular network (Verizon, non-static).
We want to access the Admin Web interface via our LAN but the BR1’s IP is not reachable. We can however access the Admin Web via Incontrol web portal.
If we change to Passtrough mode on the BR1, will we then be able to access the admin page from the LAN?
If so, are there any downsides to passthrough mode?
Thank you for any help on this question.

Pass thru mode won’t achieve what you want.
Let me see if I can make a picture of the setup, can you tell me the following.
What is the LAN IP of the Meraki?
What is the WAN IP of the Meraki (2nd WAN?
What is the LAN IP of the Peplink?
What is the IP of one of the devices on your LAN that wants to access the peplink?