1. At what image width do you draw and to what width do you decrease it after completing?
My finished (formatted for book) pages are 6" x 9" at 400dpi.
For Webtoons & Tapas, I flatten the art then cut and paste it (rearranging and slicing frames as necessary) onto a long file 1000px wide x whatever the length the episode requires.
Then when I save that file as a jpg I resize it to 800px. This way I find I don't usually need to resize the images too much; I try to crop larger panels into several smaller, scrollable shots rather than shrinking it way down to fit the narrow width.
2. At what dpi do you draw?
400dpi pages, long episodes are 300dpi, I think?
3. Do you add text before or after decreasing the image size?
I put all of the text into my 6"x9" page, then copy/paste the whole folder of text and balloons into the long, 100px wide episode and re-arrange the balloons to fit that layout. This way all my text is the same size, even if I resized the artwork.
4. What font size do you use?
I use Milk Mustache (from Blambot) size 10, though I'm not sure exactly what size that translates into once I've shrunk my episode file from 1000px to 800px...
5. Since Webtoons accepts only jpegs, do you do anything specific to make the image quality as lossless as possible?
I actually bring the quality down to 90 when I save the webtoon-ready file, because otherwise the episode will exceed the maximum file size limit. I haven't noticed that it makes much of a difference in the quality.
6. Post your Webtoon, please.