Main takeaways:
1- Some is okay, too much is bad. (But of course that's always subjective.)
2- "Live out loud"--I think this is the most helpful bit. When you use your phone or tablet, explain what you're doing, because it isn't obvious: "I am checking this recipe for what ingredients we need," and even "I opened the news app because I was bored, but it didn't really make me feel any better for doing it."
3- Age 10 (and around, I assume) is a groundswell of difference. You can think you're doing great, but before then you are the one with access and control of media. Once they are able to navigate tech without you, and once their friends become greater magnets than you, the rules become less important than the principles you've instilled. So instill them early, before 10, for best results.
4- Everyone will have screentime. You might not even own a TV, but school, friends, others will provide screen access.
5- Teach your kids how manipulation comes through the design of the screens: "This app says it's free, but it will want you to buy more things inside of the app," or "I know it's hard to end this game--it doesn't have a clear stopping point, so it makes our brains want to keep going until we drop."