VLAN only on the 2.4ghz ssid

Vlan question is it possible to use a VLAN on my pfSense box to my 2.4 ghz openwrt only ssid
You see I have a member of my family who bought a bunch of chinese smart smart bulbs and he put them all on my 2.4ghz ssid and I would like to isolate it from the rest of my network including my 5ghz ssid

Sure... If your AP has two radios, you only setup the SSID and network association with the 2.4G radio. That said, from the perspective of connectivity for 2.4G devices, there is no harm in having both radios active... the 2.4GHz devices will see and connect to the appropriate radio (they will be unaware of the 5G radio). But if you don't need a 5GHz IoT SSID, you can do just the one radio.

What I need to know is how I put the Qualcomm Atheros QCA9560 802.11bgn
radio1 bssid on my VLAN, I have had success putting a Linux VM on the same VLAN ( without needing a managed switch so I think it may be possible for me to do the same on my openwrt ap TP-Link Archer C7 but leaving the Qualcomm Atheros QCA9880 802.11nac radio0 on my main network

It's pretty simple -- just add the VLAN on your C7 (I think it's using swconfig syntax), then put that into a bridge. Create an unmanaged network interface with that bridge. Finally, create an SSID under your 2.4G radio that is linked to the network interface for the new VLAN.