I'm using Tick Tick. I like the user interface and the free features are more than enough for me. Your Google calendar can also subscribe your your task lists if you need calendar integration.
My tasklist needs are pretty basic, so I use Tasks, since it syncs with the ancient Google Tasks feature (which I'm willing to bet Google will eliminate some time in the near future, in favor of Google Home).
I use Tasks: Astrid To Do List Clone. I also have and like Sol Calendar, which has a to-do widget. Both sync with Google so I can use whichever widget goes with my theme.