Mine would be
1- One separate GSC per domain
2- One separate GA per domain
3- anonymous whois registation
4- different hosting ip
Seperare email, GSC and GA accounts for your domain names are good steps.
But that's not really how google finds out PBNs.
The most obvious signal amateur PBN runners ignore is their linking patterns. If you are not being cautious, you leak out enough info for anyone with a crawler to figure out that you run a PBN.
Imagine this, your network has 20 sites. Site A is your money site, with the most link-juice and the most valuable backlinks. Site B is your "secondary". Its not pure spam, but it's not as valuable as site A.
And the remaining sites exist to collect links. You link them all across each other and eventually pass site A's link juice across your network.
What amateurs don't get right is that they leave hapazard footprints all across the place. They will run automated linking tools to link their pages, the sites will all look similar, and sometimes there will be rookie mistakes like a common tracking url/ad-code or CDN link.
All of these are signals that you can train ml models for.
Remember that Google has more data about website backlink profiles than any other company on the planet. If small companies can figure this shit out, google definitely can.
A travel website won't just randomly link to a cooking blog, topical clustering is important what matters most running a good PBN is how natural all your sites look. Basically all websites in a good PBN network should be money site quality.
@splishsplash has quite a few guides here detailing this. You can check them out.
