Firewall and NAT for LTE in front of a router

RouterOS Beginner Basics
1

I have installed an LTE modem (SXT-R) which is connected to an RB2011.
Regarding Firewall rules there is then the option to put these on the LTE modem or on the router behind the LTE modem.
Imho it would be more logical to put them on the LTE modem which is the first part of the network looked at from the outside world.

Can anyone please advise me on this issue.
Thanks

2

When you do a DNAT all traffic from lte1 to second router or do just a LTE Passthrough then your all “Incomming from Internet” firewall rules must be at second device.
I hope this is answer. Your question is hard to read.