To find influencers with a Youtube or Podcast channel, you should use the filtering functions in the search.
Choose the "Channel" Filter, and select either "Podcast" or "Youtube".
You now have 2 options for narrowing down the topics you want to find influencers on.
Use a boolean query like you would usually to find influencers who have mentioned your key terms and also have a Podcast or Youtube channel.
Your results will be ranked according to number of mentions of the keywords, with a greater weighting towards mentions in the video or episode title.
Alternatively, you can search for influencers based on the category their Podcast or Youtube channel falls into. Onalytica uses a similar taxonomy to iTunes & Youtube for this, so simply choose either the "Podcast Category" or "Youtube Category" filter and select the options you want, e.g. "Finance" or "Technology"
You can run these with or without an accompanying boolean, but bear in mind this will restrict the number of results in smaller categories. We'd recommend running these category searches on their own, then adding bio or content searches to narrow down your results if needed.