Since Tapas didn't post an example pitch (as far as I'm aware), nobody can tell you what the best pitch would look like. I can give you insight on what I did or how I would do it again. I have a comic, so there are differences for novels, but the basic idea is the same.
When I submitted, I only summarized my first arc since it was enough for one season for Tapas. I did mention the other arcs, but did not go into details. I recommend this summary to be as tight and short as possible, as your outline will go more into plot point details. In the summary, I tried to do something similar to the plot outline on the back of a DVD cover or a book - I wanted to hook the reader (Tapas editor) to be interested and invested in the story.
If you seriously want to proceed getting your work published, it is time to get it digitalized. You may also want to consider updating your episodes to the 2nd draft, if it is different and the way you want to move forward.
What you put online is technically considered your final version, and trying to explain that what is uploaded so far isn't actually ready may be confusing for the other party.
Mine were too - and I'm pretty sure my outline was really shitty... Luckily my summary (and sample chapters) were better. They didn't seem to mind the bullet points, and I still think it's the best way to share a long story.
Make sure you're confident in your story and have a clean pitch before you send it. Let others read it and critique it, to make sure everything makes sense, has no grammatical errors or typos. Ask them if they would read a book with this content. (I did none of those things because I was an idiot.)
If you had a comic, I would also recommend to do character designs and banner artwork, but this doesn't seem to be necessary for novels.
Happy writing and good luck!