You have to use the --agent-dir argument for the node installer to deploy oneagent to different directory on cluster node.
I think the /opt/dynatrace/oneagent symlink has to stay there.
About /opt/dtrun I'm not sure, looks as a temporary directory created at installation/upgrade time. I think this will be recreated during cluster upgrade anyway.
Since this does not take almost any space in /opt - is there a reason for deleting this stuff?