Removing by ADB is fine if you are able to identify which packages should be removed or if they’re already covered by Universal Debloater. You should also use Invizible Pro to control what connections are made and block trackers.

It’s unclear to me how these torrents are used. If individual books are not downloaded from them, is this only to make it possible to create similar sites in the future, in case this one is taken down?

You can make stock Android much more private. Universal debloat tool + Invisible Pro - remove unnecessary apps, restrict internet access to only the apps you want to have internet access, add a tracker blocker list.