Timestamp, source and destination ip addresses, username. In the case of the exit node, url.

We don’t know that Apple keeps logs. These are things they could theoretically keep, but we don’t know if they store them or not.

If they don’t clearly state ‘no logs’ then its unlikely they are not logging. My bet is they’re logging everything, because they have no advantage in not logging.

Only the timestamp and username would be available from Apple.

Source IP address and next-hop IP address would be as well.

Source on the next hop address?

Apple doesn’t know where you’re going.

They shouldn't know about the end destination, but they'll know your traffic was sent to eg. Cloudflare or whatever.

I would think they batch together all the IPs and pass it off.

It's in Apple's best interest to keep the bare minimum information they need from their end-user.