If you're adding view transitions to your sites, the Material Design guides have some great examples, and some patterns to avoid. I don't think their word is law, but there are a lot of good ideas here.

https://m3.material.io/styles/motion/transitions/applying-transitions

Transitions – Material Design 3

Transitions help guide users as they navigate an app.

Material Design
Probably the most important point to consider is "unified direction". It's very tempting, and easy with view transitions, to transition every 'element' that exists in both states. But that isn't always the best idea: https://m3.material.io/styles/motion/transitions/applying-transitions#b974d94c-bf80-4c54-8818-4a1d7eaa10ae
Transitions – Material Design 3

Transitions help guide users as they navigate an app.

Material Design
@jaffathecake these look lovely… but the thing that's always tripped me is up on these examples is visualising the code that would achieve that full effect (and indeed the actual backend pages, or at they nested… or something else).