OPNsense on TrueNAS Scale server - best practice

[alexgee]

Dear all,

I'm a total OPNsense (and TrueNAS) noob, but I got convinced to try the OPNsense route instead of an off-the-shelf router.

My planned setup:
LTE Modem (Router in Bridge Mode)
Server with TrueNAS Scale (2x Intel i210 NIC & 2x Intel X520 NIC)
Switch, etc.

I want to use the server to run OPNsense, dedicating the 2x i210 NICs.
If I'm correct, the modem will go into one NIC -> FW -> Output other NIC to switch. Main connection of all other server activities via X520 10GBE SFP+ to switch.

Please correct me, if the hardware setup is nonsense...

Software:
I have installed TrueNAS Scale and I suppose to install OPNsense in an own VM.
Correct?

Are there any good guides for the installation?
I have downloaded the dvd-iso of OPNsense - is it possible to install it directly, or on top of Linux, or FreeBSD?

Thank you for directing me into the right direction.
Alexander