Yes — set the source language in advanced options so the recognizer loads the right model. Matching the language to the WebM audio noticeably improves the HLS transcript quality.
Yes — a transcript HLS is real text, so you can edit, correct, search, and copy from it. That is the point of turning a WebM video into a document rather than leaving it as a media file.
Can I get subtitles instead of a plain HLS transcript?
+
For caption-style output, use the dedicated subtitle tool which emits SRT / VTT timed to the video. This WebM to HLS flow focuses on a document — a plain transcript or a frame contact sheet.