To answer the first, strangly enough no. You would think if you intensionaly disable a protocol you just don't want logging to give errors about that. If you look at the logging the real important errors are shownin the first portion. under the ********* Additional results (listed for information only): line the info is optional and only needed for troubleshooting identification issues.
For Agentless monitoring you don't need extra licences. For once it's free. Don't forget to uninstall the agents, the export the nodes, delete them and re-add as SIM remebers this it was able to use the old protocols.