Guidance on AP Mesh Setup for Deco S4

Good evening all. I am looking for some guidance on a proposed mesh setup. I have 3 TP-Link Deco S4 that I would like to install OpenWrt. Right now, they are running stock firmware in AP mode as I have the main Deco connected to an OPNSense router. I would like to use OpenWrt to have 3 SSIDs - one for regular LAN, one for IOT devices and one for guests. I’d like to set up 3 VLANs to separate the traffic (and have rules on the OPNSense router to keep each VLAN separate). So, each of the Decos would still be an access point - one hardwired to the router and the other two as Wi-Fi mesh nodes.

I see a lot of videos on how to set up a mesh but it assumes one of the nodes would be a router. I am looking for some guidance for the setup of all 3 as an AP with multiple SSIDs. Is it as simple as setting up 3 SSIDs with their own VLAN and setting up an 802.11s mesh with the interface tagged with each VLAN? Do I need to look at Batman-Adv? I’m probably missing something or have got my understanding all wrong so any help would be appreciated.

Thank you in advance.

Table of Hardware

That router is supported at the snapshot level. It says no LuCI support (GUI) so I would wait on that if you are new to OpenWrt or if you want a quick easy solution. This would be harder to do at this time (all command line with VI text editor) or may not work perfectly as it is in development - unless you want to help testing for development. You would need batman for multiple vlans.

That device only has 16/128mb of memory so also consider the following: