[zamadatix]

> For example if your ISP gives you /64 prefix, most consumer routers will not recognize it as valid.

A /64 is the most valid IPv4 prefix there is. Most consumers should be given multiple (usually about 16) and the router starts with the first one.

> And if you get a /128 prefix, good luck that

No kidding, that's a single address subnet!

> NATs are apparently disallowed in IPV6 world.

It's allowed it's just not the right answer in the vast majority of cases.