Setup security concept in homelab with network segmenation and 2 firewalls

Hello,

I want to setup a security concept in my homelab; if required I could 
share a document that illustrates this concept.
There should be 2 firewalls with different software stack.

I have a device 
<http://cdn.cnetcontent.com/a7/17/a7178a00-966f-47ba-a44d-8e229f23f978.pdf> 
with 4 NICs that is running OPNsense <https://opnsense.org/>; this 
device should be used as router + firewall. And this includes a WAN port 
connected to my ISP modem.
The plugins available in OPNsense allows to offer additional services, 
e.g. reverse proxy, HTTP proxy + AV, DNS (with webfilter).

The other firewall will be deployed in a VM using Shorewall; this VM can 
have as many NICs as required.

What I don't understand is if this concept would work in general.
And I don't know if it's correct to configure all interfaces and its 
network segments in OPNsense (by using available NICs + VLANs).
Which interfaces would be required for Shorewall VM?

I would appreciate your advise.

Regards
Thomas