You find out the addresses after it is configured automatically. This is no different than IPv4 and DHCP.

If you don't want to use the public addresses internally, then you can assign ULA addresses. If you don't want to use MAC derived addresses, assign them static host addresses.

For names, I use mDNS. I don't know the IPv6 address for my server. If I did need it, I would get it from the router.