Hi - i'd say a mix of both, we've lost a couple department stores due to insolvency (Beales / Debenhams - although the latter being re-purposed currently)and the likes of M&S have moved out of the centre. Shops are mainly fast fashion (Zara/Primark/H&M) and a mix of others, but quite a limited selection considering the size of the area in my view. I'd say there are some social issues as well, for example a noticeable number of people/groups with apparent alcohol dependencies in the centre (although they generally keep to themselves). Wouldn't want to be too negative though, it's fine, nice in parts and has attracted investment.
For tourists you just have to accept in the summer hols it'll get busy here and adapt accordingly, the high street is busy, the beach can be packed (i live a few mins walk from the beach and don't go down some days) and traffic can be an issue if you time it wrong.
If my fx is correct a million aussie is about £520k? If that's right, you could definitely find a decent house in a nice area. Depends what you like of course, check out 1) Southbourne decent selection of cafes on the high street, near a quieter section of the beach (Hengistbury Head near there always reminds me of Australia as well) for much more sensible house prices (although prices have gone up a lot), 2) Christchurch, which gets busy in the summer but is pretty with a good little high street, 3) Talbot Woods/Meyrick Park - attractive area with some really good houses/roads and not too far from the beach, 4) Ringwood - c.15mins drive from Bournemouth, but an attractive town near the new forest.
Definitely would agree with you that worth spending some time here to see what area you like, there are plenty of good options. Good luck if you decide to move here!