I think you're slightly off on that first one. Killing 3rs party cookies isn't anti-competitive, in fact I'd argue any decent browser should do it to protect their users' privacy.
What is possibly anti-competitive is their proposed alternative. And frankly I'm not sold on the supposed privacy of such an alternative either (which, in order to be functionally different from 3rd party cookies, will have to store personal identifying information in a location that users cannot access, edit and/or control).
Note also that (to my knowledge) browsers are not currently obligated to protect their users' privacy (though perhaps they should be, it makes more sense than punishing websites for sending cookies). This leaves google at least 2 completely legitimate options:
1. Keep 3rd party cookies.
2. Kill 3rd party cookies.
Sure the first will cost them their privacy conscious users and the second might hurt their ad business, but rejecting that choice on the sole grounds that it would hurt the bottom line of a different venture is textbook anti-trust. They'll probably list other reasons for not taking that second option, though I've not found them terribly convincing so far.