The routing is completely reworked. It is easier to understand than in the past, but it uses very different philosophy. You need to apply the routing on each repository manually. Thus you can not have more routings per repository.
And you have two possibilites: block (block everything mentioned in the patterns) or allow (block everything, that is not in the patterns).
If you migrated from NXRM2, your old routings will be ignored (which I did not notice and it caused huge problems to stability of our Nexus).