I looked briefly at one PC like that. 15w of power looks great but from other hand 2 nvme disk 6tb Max total does not looks that great anymore. You have to have some other PC or Nas for backup at the least.

Depends on the purpose. Maybe not the best for very big NAS with 10G ethernet requirement but suitable for many other purposes. Maybe you don't need that much space or maybe you are just running git server.

What on earth do you need more than 6tb internal storage for!? It has ports aplenty and external storage is cheap cheap cheap these days. Mine streams 4K media via externals without breaking a sweat