From "PC" to igb1 to firewall (localhost) to igb2 (WAN) - ehhh ????

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I think I am making it harder for my self than I should - however the only way to find out is either to test and test, or ask? So I ask:

What am I thinking wrong here?

My firewall is a Qotom-Q555G6 based box, so 6 ethernet ports. Currently I seem to use them more as an expensive switch, however that will not be the case in the near feature - but before that I need to understand the last bits of how the firewall behaves so to speak. So this is how I use the 6 interfaces:
igb0 - LAN, or the main PC
igb1 - WAN (FTTH)
igb2 - WAN Backup (Netgear M1 LTE modem (MR1100))
igb3 - PrinterScanner
igb4 - MediaWiFi (all media components and a WiFi AP)
igb5 - Server (LMS8 media server and HomeSeer3 home automation server)

Now here is what I still don't seem to get right: In and Out of different interfaces in combination....

Example 1 - If I send something, like a URL to internet, from that PC, it will go from:
PC -> (in) igb0 (LAN) firewall for LAN (out) -> (in) igb1 (WAN) firewall for WAN (out) -> Internet

Example 2- If I send something local, like url to my LMS server, it will go from:
PC -> (in) igb0 (LAN) firewall for LAN (out) -> (in) igb5 () firewall for Server (out) -> server

What I am not sure about is that middle part, which I hope I am making over complex: From the PC -> into firewall and then out direct to say WAN, and not the extra out/in? Or ehh? it just spinns for the moment - maybe someone can stop my head from spinning?

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I think my post in another thread says it all:

https://forum.opnsense.org/index.php?topic=18355.msg84022#msg84022