Asus have given you the correct information. All you need now is your PPPoE login details from vodafone via this link (avoids the dumb ai questions)
https://vodafone.co.uk/bbservcd
Your username needs to be entered in the format dslXXXXXXXXX@broadband.vodafone.co.uk
If you're on an openreach connection there's no vlanid to enter, for cityfibre it's 911 - this may be automatically done for you, otherwise it's in LAN>IPTV.
AX16000 - great choice for 900Mb.
