Hifiberry Amp2 Install

[pimseb]

Hello
I've bought a HifiBerry Amp2 and I'll receive it tomorrow. I'll use it with an USB microphone.
I'd like to install Alexa and Google assistant on it but I'm not sure about the sound script I should use.
When I read The Hifiberry documentation I see I need to change config.txt file this way :
#dtparam=audio=on #to disable onboard audio card
dtoverlay=hifiberry-dacplus

And then I must change the asound.conf file to :

pcm.!default {
type hw card 0
}
ctl.!default {
type hw card 0
}

But this way the asound.conf does look different that the one I see in Assistants-Pi/audio-drivers/CUSTOM-VOICE-HAT or in USB-DAC (I don't understand the pcm.dsnooper part)

Can you tell me how should look my .asoundrc file and /etc/asound.conf files ?
Thank you