[3np]

PCEngines APU for DIY, or Mikrotik for a provided solution. If you need more ports or throughput, extend with a dedicated switch. Any stupid unmanaged switch is good enough for most SOHO use-cases, unless you want to get serious with segmenting your network with VLANs and ACLs.

As for what DIY OS/dist, I have used VyOS, IPFire, pfSense, OPNSense, and a handful of various xx-WRT derivatives. OpenWrt is still my recommendation without a doubt. I'm still not at all a fan of the update and package management of OpenWRT, but it's the best out there unless you configure a vanilla debian install yourself.

Keep WiFi APs as separate devices, regardless of if you mesh or not.