With containers, most will have a persistent volume that is mapped to the host filesystem. This is where your config data is. When you update a container, just the image is updated(pihole binaries) but it leaves the config files there. Things like your block lists and custom dns settings, theme settings, all of that will remain.
Their android app is total garbage and frustrates me to no end. I’m seriously considering just going back to pirating my music just because I hate spotifys music app…