A somewhat oversimplified summary of the new UUID formats:
UUID6: a timestamp with a weird epoch and 100 ns precision like in UUID1, but in a big-endian order that sorts naturally by time, plus some random bits instead of a predictable MAC address.
UUID7: like UUID6, but uses normal Unix timestamps and allows more timestamp precision.
UUID8: like UUID7, but relaxes requirements on where the timestamp is coming from. Want to use a custom epoch or NTP timestamps or something? UUID8 allows it for the sake of flexibility and future-proofing, but the downside is that there's no standard way to parse the time from one of these -- the time source could be anything monotonic.
UUID6: a timestamp with a weird epoch and 100 ns precision like in UUID1, but in a big-endian order that sorts naturally by time, plus some random bits instead of a predictable MAC address.
UUID7: like UUID6, but uses normal Unix timestamps and allows more timestamp precision.
UUID8: like UUID7, but relaxes requirements on where the timestamp is coming from. Want to use a custom epoch or NTP timestamps or something? UUID8 allows it for the sake of flexibility and future-proofing, but the downside is that there's no standard way to parse the time from one of these -- the time source could be anything monotonic.