Rooting is not required, using Blokada, you use a defined set of filter lists, some of them, included some known facebook domains already, even if they are not for social, e.g. graph.facebook.com
In the case of AdGuard, rooting is used in the tentative to not display ads on YouTube app, or set the process priority to the lowest possible to stay always on.
The difference, when comparing AdGuard to Blokada, at least in my experience, is AdGuard capability of displaying the logs, and cosmetic filtering, means CSS stuff on mobile, you can do with AdGuard, both of them rely on the VPN filtering;
What I usually do, from time to time I install Blokada, and take a look at their lists, then, I add them to my PiHole; the main problem is the huge number of domains contained inside the blacklists, that then i need to whitelist
For example: AdGuard, will be able to do this --> astronomy.com##.facebookFeed
where, Blokada not
both of them, will be able to block the domain graph.facebook.com if is inside the rules.