Home network design - new to OpenWRT

I'm a newbie to openwrt world and looking to build a home mesh. I wanted to list my design goals to see if I'm on the right path:

  1. Wired 1Gbps egress to my internet router
  2. Granular Firewall and Flow Monitoring w/o sacrificing too much speed
  3. Mesh network of nodes (wired or wireless back haul) throughout the house

Bonus points:

  1. Multiple SSID - Perhaps I can use the old devices to hang off the new ?
  2. VPN or Wireguard for specific AP clients (or SSID)

I'm thinking of using:

  1. GL-B1300 for each floor, reflashed to a newer openwrt for primary devices
  2. old nodes or rpi4 running openwrt for IOT

I had also considered a Fortigate 60-series on the north side of a cheaper end, but if OpenWRT can do the trick that'd be grand.

Feedback appreciated.