Hi. we never used that plugin so you need to found out by yourself.
with pluto we have a vanilla installation of mythtv and wrapers that send the commands from orbiter to mthtv.
about xbox and tivo; we didn't add specific support for them, our intention is to have support for a wide range of hw. i guess if you can make debian run on them, they can be controled in pluto. again, we didn't test this hw, you'll find more info on forum, if you have the patience to search.
our asterisk is vanilla with some patches. We are using asterisk + AMP + some custom scripts.
i don't know what smoothwall is. pluto can be installed with one and with two nics. depends on the installation, the core need a 2nd card to give dhcp to other devices on lan.
yes, you can install pluto without capture cards.