Welcomix review
Welcomix publishes illustrated comics with an index organized around recurring series. Its public terms describe access as a personal-use licence to a catalog of original or licensed work.
What the series index shows
The All Series page gives each series its own entry and description. The homepage advertises weekly updates. The terms describe a recurring subscription for access to the illustrated catalog.
Finding a finished run
Yumeku lets you filter for completed stories and inspect the episode list. If you want a finished run, that filter gives you a starting point. At Welcomix you can choose a series by its description and check which issues are available before subscribing.
Anabel’s take
I'd browse Welcomix by series and choose one I actually wanted to follow. If I were interested in a single finished run, I'd want to know how many of its issues were available before subscribing.