I just started diving into i3 a few weeks ago. This is using a VMWare Fusion VM and Fedora 31. So I'm not fully evaluating things like volume, brightness, but battery/charging indicators work. Most of the instructions I followed were ~4 years old and worked almost out of the box. A few minor things have changed, like most people have switched from Compton to Picom, but the old packages are still there and work (unless you need newer features/bugfixes).

Windows seem to work as expected. Dialogs/pop ups show up as floating windows, but everything else worked well as a tiled window. Fullscreen worked fine. I haven't used a wide variety of apps. Mostly a few browsers and terminals, but I was doing some Qt dev in it, so I was playing a bit with windowing.

> Is it now easy to set up a launcher/start bar...That work both when I click on them and via keys...

From what I've seen of i3, all of the status bars are text printed from a separate program that gets executed periodically. This makes it very flexible and with things like font-awesome you can have emoji and icons, but afaik you can't click or have pop ups. Other tiling WMs, like AwesomeWM, will do this.