Re: Two questions if I may
A users ip6 address is much more likely to be static that their ip4 address
The 20th century called and asked for it's Old Wives Tale back.
"Fixed" IPv6 addresses (aka EUI-64, IIRC) were deprecated years ago for exactly that reason. Now the standard is for devices to generate (multiple) random addresses within the 2^64 address space available to it and to change them over time. Tracking by IPv6 address is impractical.
You can track by /64 netblock, but then you get no more information than by tracking a network of devices behind a NAT gateway. My IPv4 address is as static as my /64 IPv6 block.
The staticness of both the IPv4 address and IPv6 allocation is not inherent in either protocol - it's entirely down to the allocation mechanism done by the ISP - in some cases you can request a static IPv4, in some you can only have a dynamic one, in some cases you can only have a static one.