Google & Youtube - unsafe to browse (privately) even on VPN?

[magnumpi 4]

So I understand that some scripts in Youtube can compromise anonymity?

I assume if you are logged into a Gmail account, Google can see your IP and then presumably share that info with other parties to identify you at other websites?

Also, I recently was testing Prey software. When enabled this turns on a Google service that is able to read your computer's nearby wifi networks!? So even if you are not using wifi, it can see what wifi networks your machine sees and pinpoint you based on that!! Is that service only able to do this when I allow it on my machine or can this be embedded into other web services I may not know about?

Do I understand all these vulnerabilities correctly? Is there anything simple I can do to combat them that would still allow me to use these websites?