A /64 is the smallest network on which you can run SLAAC, so almost all VLANs should use this. /56 and /48 for end users is what RIRs are recommending, in reality the prefixes are longer, because ISPs and hosting providers wants you to pay like IPv6 space is some scarse resource.

[1]: https://www.ripe.net/publications/docs/ripe-690/

Everyone at my isp is issued a /56 (and as far as I can tell, the entire country is this way).