Also recommend https://nextdns.io/ which supports common ad block lists, etc. I have my home router and phone set to it and is crazy how many trackers and ads are blocked.

Seems to be a good service to me. There seem to have been some complaints recently, though: https://www.reddit.com/r/nextdns/comments/ju2hfw/nextdns_pri...

NetGuard is great, it can show you the requests done by any apps. Thx to it, I discovered that my default camera app on my phone was sending data to Facebook and many other quite concerning stuff.

Internet access should be a permission (like camera, mic, etc.) unfortunately in Android it isn't the case and any app can communicate with any server. With NetGuard you can decide which app can access internet or not.

Does Netguard require to be rooted? Does it show the traffic per app?

It does not require rooting. It shows connnections per app, and how much data has been transferred to each of those connections.

What I tend to do is: install an app → block it before running it the first time → look at every connection attempt made (usually first through ipv4) → wait a bit more until apps attempt connection through different protocol (ipv6 or U) → block anything I don't like, including ads, analytics, etc → tell NetGuard to now allow the "legit" connections to be made and start using the app.