8 Interfaces vs 4 w/ a switch

So I have a custom PC running now running XG and 4 interfaces seem to be working well initially at least

1 WAN

1st LAN (with a switch)

1 Wifi (AP100C)

2nd LAN (probably will just be for management)

I'd like to add a 2nd 4 port NIC (Intel, so is the current card) instead of using the switch as it is needed elsewhere.

I'm thinking that this would help me have a LAN for TVs, a LAN for PCs without communication between devices, and a LAN joined (bridged?) to a 2nd Wifi SSID LAN where people can temporarily connect to it to use an old network printer.

I am thinking that works pretty well for isolating devices\groups of devices and I wouldn't have to use VLANS. Any problems with this idea?  I have not dived into the firewall rules and IPS yet, honestly a little leary of it all. Just want to make sure this would work before buying a 2nd NIC.  Thanks

Also, my father has a three employee business (only him full time) and I would like to consider building a set of hardware for his office. Are there any economical routes for this size of business? Kind of hard to justify big subscriptions and don't want to go against Sophos's commercial policy. Thanks

Matt