Soundiiz is only able to do a matching process between source metadatas and destination catalog.
When dealing with "YouTube", only the title of the video is used, which could cause many elements not found in the destination platform. If you are having music videos in your YouTube playlist, we recommend you to connect "YouTube Music" on Soundiiz instead of "YouTube". We will be able to retrieve more metadatas and so, getting a better matching result.
There's no requirements to have a YouTube Music subscription to connect YouTube Music on Soundiiz. More information here: Differences between YouTube and YouTube Music on Soundiiz