Optimal way to utilize two RPi 4

Hello all, hoping it’s okay to ask here, what is the optimal way to utilize two RPi4s for HA? Is there a more efficient way to using them together than running two seperate HassOS-instances?

I have two RPi 4 with 4gb RAM each, one in an Argon M2 casing with 256gb SSD and the other without a casing but with a PoE HAT with a fan with a 500gb SSD connected with a powered adapter with USB 3.0. In addition a Aeotec Z-wave-stick connected to the first one by an extension to USB 3.0.

I’m running (amongst other) the following add-ons with HassOS:

  • Nginx Proxy
  • AdGuard DNS
  • MotionEye (3 mjpeg-cameras)
  • Android Debug Bridge
  • MQTT Broker/client
  • Music Player Daemon
  • Grocy
  • Samba Share
  • MariaDB
    Also running (amongst other) following integrations:
  • Google Wifi
  • Google Cast
  • Philips Hue
  • Tuya
  • Tapo Camera
  • Z-Wave
  • Spotify

A lot of automation with lights, alarm, CCTV, media players, dishwasher/washing machine etc. etc. etc.

Originally running this on a single RPi4 did ultimately keep pushing the CPU and memory-usage above what was healthy in a long term, also pushing the temps. a bit, but not much. As I had another RPi4 laying around I configured it as a secondary HA-instance connected to the first one with remote HA and moved Nginx, Adguard, MotionEye, MariaDB, ADB and some other services to that one.

This distributed the load nicely amongst the two, but it’s proving troublesome running two seperate instances with managing them and getting access to services/files back and forth.

Yeah, it would be cool to have Docker swarm support in HA, but I guess that’s not gonna happen, as Docker is basically dead.
So the other option is to move from the dying Docker to e.g. k3s and that would give us the ability to add more nodes to the HA and have it more reliable and be able to spread the load over few small SBCs, instead of building something beefier with beefy power consumption.