Since I'm likely going to become the resident expert here on all things NBC Olympics, here's what I've gathered on Peacock..
There are 3 tiers of service. A lot of the content is available for free, but it will be ad-supported. That includes things like libraries of old TV shows, plus access to next day airings of shows on NBC. Then there's the paid tier. $5 gets you additional content which will include among other things, access to NBC late night shows before they air on late night (i.e. Jimmy Fallon and Seth Meyers). And the third tier is $10. That's the same as the $5 tier, except it is ad free.
In terms of Olympic content, Peacock will have exclusive streaming of the Opening and Closing Ceremonies. I'm guessing that means it will NOT be available on the Sports app, although to my knowledge, that's where all the event streaming will come from. So that, as usual, will be tied to whether or not you have a cable subscription. But there will be additional programming exclusive to Peacock. No idea at the moment if this will be on the free tier or only as part of the paid service..
Plus, it sounds like Peacock will have all the live streaming of the Paralympics. They're promising more than 1,000 hours. And I have a feeling they'll continue to grow as we get closer to Beijing.
Don't know if I'll become a regular subscriber, but I'll gladly pay $10 for a month to get all that!