> Also structure-wise the first half is the subnet and the second half is the host. That's much more intuitive than IPv4.

This only applies to /64 blocks, which are by no means standard. For instance, tunnelbroker.net will give you a /48 for free. This means IPv6 addresses are essentially free by the billions, but it's difficult to figure out how big of a block they belong to from the outside.

Regardless of the prefix size, a subnet is always /64 in IPv6. A shorter prefix simply means you can have more /64 subnets.