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I missed one question you asked - as Google is unable to index content which is only available for registered users I might be a good idea to create a preview page - showing part of the content even when not logged-in. This only makes sense however if the content remains interesting enough for visitors even if only part of it is accessible. You risk to get a high bounce rate on these pages, as the content really needs to be very unique and valuable for the users in order to go through the complicated process of registration. Personally, I always get frustrated when landing on these kind of pages, and unless it's a site that also seems useful for future visits, I always go back to the search results and try to find other sites which provide the info without registration.