I have a bit of experience with Webtoon so I think I will also chime in : D
In my experience, I generally found the best time to post is 4PM - 6PM (GMT-6) since that is when a lot of readers in America (it is LINE Webtoon English after all) are getting off from school, or peps with works get off from work.
Also if you want to announce a fixed day you will be updating, don't forget to include your timezone! I learned this the hard way after many comments later saying "It's already past the promised day" because there are a lot of readers that read English Webtoon who live on the other side of the planet, which means typically 10+ hours ahead.
A good way to make friends either on Tapas or Webtoon is just follow creators on their social media, draw fanart for them, write fanfic, etc, leave a nice comment on other people's stuffs. I also find out that when I do QA and listed out what comic in the Discover section I enjoy (low key promoting/advertising without really asking for anything in return), those creators tend to end up finding me too and express that they also enjoy my comic and that was how we became friends!