Hello,
The plugin does not do multisig, nor does it do mixing, at least not intentionally.
Because all users share the same wallet, a user could deposit an amount, and then withdraw that same amount, and the amount could be mixed: i.e. the withdrawal could come from one or more UTXO addresses (corresponding to deposits from other users). But this is NOT guaranteed, so you cannot say that the plugin does mixing.
Of course, if you were to use the Monero adapter or the TurtleCoin adapter, these are privacy coins that do mixing by default. So in that case you have the mixing feature (but not multisig).
Hope this helps. If you have any other queries about the plugin, please open a new thread.
with regards