Yes, the destroyer wrecks are very close to HMS Bristol.
Nick, re HMAS Sydney, I rather doubt if there was another raider involved in the action. There are some very interesting reports online about the circumstances of the ship's loss and her rediscovery.
Very briefly, as you will know, the Australian captain let his guard down so Kormoran had the advantage of surprise and got the first shots in, one of them destroying Sydney's bridge, probably killing most of the senior officers and knocking out her fire control. Further hits disabled the forward turrets and a torpedo pretty much blew off the bow. It was one of Sydney's after turrets, X I think, which actually scored the hits that eventually sunk Kormoran firing in local control at her waterline.
Although it seems an unequal encounter, the odds were actually much more balanced than you might suppose. Kormoran had at lest three 5.9s able to bear on Sydney while the cruiser, with perhaps half her main armament out of action and not under command after the initial surprise was unable to make an effective defence except for X turret. The range was short so it is probable that Kormoran's lighter armament interfered with attempts to use the Sydney's 4 inch guns which were reportedly not manned at the commencement of the action.
Light cruisers had very little armour, just a thin belt and magazine protection while the gunhouses were only splinterproof.
The facts, insofar as they are known, are quite well summed up in the Wiki article
https://en.wikipedia.org/wiki/Battle_between_HMAS_Sydney_and_German_auxiliary_cruiser_Kormoran which draws on a number of sources and appears to be consistent with the state of Sydney's wreck.
Colin