Questions for use in a Carputer

I want to use this as the brain for a Carputer but I have some
1: I want this to power on and off with ignition, is there a way to do that
with this board? I'm sure I'll need a relay attached to the switched 12v
that'll feed the 12v to 5v converter but where/how can I connect that to
the board so it'll turn on? Also how would I turn it back off, as I'm sure
just cutting the power to the board will eventually damage it?
2: I want to use a touch screen(I see the output for it) but also want to
use the HDMI for the sound to the amplifier( using a HDMI to AV converter
like this one:
). My question is will the computer allow me to use both the lcd output and
HDMI output?

Thanks yall