For SWE
Your own
The one that pays the most or the one that you own
It's not as important as you think.
ACME Corp
Amazon
Depends on who's reading. A technical person will respect Datadog the most. A layperson (aka recruiter) will probably be more impressed by Lyft or Pinterest.
That's not true. All depends in what you do in any of these companies. What exactly is special about datadog. I am at AWS and even from team to team is a different world.
Pinterest by far
Albertsons