My question is how can it dock with other craft? Can other vessels like Constellations, Retaliators, Redeemers etc with an extendable docking collar match up with a Vanguard?

The Vanguard is designed for landing rather than on-orbit rendezvous. As such, it does not have a ring for ship-to-ship docking. (It can still be boarded, or manually exited... but both will involve EVA.)