It's also a for-profit company and you're not the customer, as you're not paying them money.
I'd be way more worried how they're using the data they're collecting on you vs Google or MS
How it works now is that when Brave replaces an ad, they put the new ad in a popup, not in-page
That's not how it works. If you turn on Brave ads, they show up every once in a while, completely independently of webpage ads. And they work whether your ad blocker is on or off.