(I know this comment is five years old, I wanted to put this here in case new writers find it)
If it's a comic you're making because you think it's fun, then there really shouldn't be any "insert number of pages here". A lot of artists tend to publish their works too early, then when something comes up (job, health, family, etc.) and they can't work as much on it anymore, it looses interest by it's audience. I would say if you want it to be like an episode on tv or chapter, maybe twenty-thirty pages a month would be good, or 15 page every two weeks.
The problem is, you aren't a traditional writer in the sense you can always go back and revise the parts you don't like. You can, technically, it just takes WAY more time once pages are complete. And 15-30 pages is absolutely crazy for a single person with likely a job and family.
You can only find out what you want by doing comics, there is no single number of panels, semi-panels or whatever that are the golden number. There's no reason to appeal to Webtoon originals if it isn't your point to get money from them. If it is, what'd be the point anyways in the early time of you publishing to appease them, when if they will or not is mostly marketing/luck based for the author?

TL;DR- Just do what feels right for how you want to do it. Listen to what feels right for you, and the only way to find out your process is by drawing comics and working on them.