The nodes will not "mirror" content of other nodes, no. The nodes will be just storing their own data + provide a UI for browsing content of that node as well as the content of other nodes. So technically you're not hosting anything illegal even if some other node does.
Freenet gets around this by having the local data store encrypted and invisible to the local user. You may or may not be hosting illegal/terrible things, but you (and more importantly, the bad guys with guns) don't know either.
