Here are two more vanishing 12-plets similar to yours:
$$ \substack{ \displaystyle{◻◻◼◻◻◻} \cr \displaystyle{◻◻◻◼◻◻} \cr \displaystyle{◻◻◼◼◼◼} \cr \displaystyle{◼◼◼◼◻◻} \cr \displaystyle{◻◻◼◻◻◻} \cr \displaystyle{◻◻◻◼◻◻} } \quad \substack{ \displaystyle{◻◻◼◻◻◻} \cr \displaystyle{◻◻◻◼◻◻} \cr \displaystyle{◻◻◼◼◼◼} \cr \displaystyle{◼◼◼◼◻◻} \cr \displaystyle{◻◻◼◻◻◻} \cr \displaystyle{◻◻◼◻◻◻} } $$
I found these using JavaLifeSearch, combined with manual filtering of the search results to skip any non-polyplet patterns. I suspect that, with your 9- and 12-plet and the 10- and 12-plets found by Noam D. Elkies, these (and their rotations and mirror images) are the only vanishing polyplets with 5 to 12 cells in Conway's Game of Life. Unfortunately, since the search tools I used aren't really designed for this specific task, I cannot absolutely guarantee that there aren't any other such polyplets that I've somehow missed.
As for your bonus question, I'm not sure what you mean by "of an other kind", but it's pretty easy to use tools like JLS to construct large vanishing polyplets with arbitrarily complex boundaries and inner structure, like this somewhat whimsical example:
$$\substack{ \displaystyle{◼◻◼◼◻◻◼◼◻◼◼◻◻◼◼◻◻◼◼◻◼◼◻◻◼◼◻◼} \cr \displaystyle{◻◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◻} \cr \displaystyle{◼◼◻◼◻◼◼◻◻◻◼◼◻◼◼◼◼◻◼◼◼◼◼◻◻◼◼◼} \cr \displaystyle{◼◼◻◼◻◼◼◻◼◼◼◼◻◼◼◼◼◻◼◼◼◼◻◼◼◻◼◼} \cr \displaystyle{◻◼◻◻◻◼◼◻◻◻◼◼◻◼◼◼◼◻◼◼◼◼◻◼◼◻◼◻} \cr \displaystyle{◼◼◻◼◻◼◼◻◼◼◼◼◻◼◼◼◼◻◼◼◼◼◻◼◼◻◼◼} \cr \displaystyle{◼◼◻◼◻◼◼◻◻◻◼◼◼◻◻◻◼◼◻◻◻◼◼◻◻◼◼◼} \cr \displaystyle{◻◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◼◻} \cr \displaystyle{◼◻◼◼◻◻◼◼◻◼◼◻◻◼◼◻◻◼◼◻◼◼◻◻◼◼◻◼} }$$