I’m guessing that a good chunk of that usage is coming from the TrueNAS VM.

Like other people have said, it’s going to depend on what you want to do with the NAS. If it’s going to be a pure NAS (ie network storage only), then using onboard will be fine. If you plan on doing other things (home assistant, media server, etc), I recommend going the virtual machine + HBA route.

I used a hodge-podge of chinesium parts and leftover drives to create a DAS system that hooks up to an HBA via DAC. I’m actually kinda surprised how stable it’s all been.