The issue with the conversations is know - unfortunately the information why conversions are new and which are not could not be imported into the new version.
It's still there. Both the option to hide signatures all together (it's at https://board.flowergame.net/index.php/Settings/) as well as the option to hide your own signature (when you create a post, use the "extended reply" button, then a settings tab appears where you can disable your own signature for a specific post).
Yes, the signature is no longer displayed in the profile. Although I don't see why it should, you have a full profile page over there.
For me, editing the profile works? Please be more specific.
Proper titles will be added. You can already see which role a user has by the background color of the users title. Regular user's title has grey background, for mods and admins it's blue.
Transparency does actually work - but the forum uses a white background for all avatars, especially the transparent ones.