There are already ways to have tiling and a DE.
On GNOME, there’s PaperWM, although it’s not quite traditional tiling either.
On KDE Plasma 5.27+, you can use Polonium. For versions before 5.27, Bismuth.
And on Xfce or LXQt, it’s often possible to use them with a traditional tiling WM, like i3wm, bspwm etc…
Krohnkite went unmaintained a while ago, which is when Bismuth forked from it. So, Bismuth is basically a straight upgrade. The dev implemented tons of features, which you may or may not need, but I think, there were also some fixes for stability and Plasma version compatibility.
Polonium came about, because Plasma 5.27 introduced a (manual) tiling system of its own, which partially broke Bismuth, but also meant it made sense to develop a new KWinScript, which makes use of this native system.
As such, it is a step back from Bismuth. I think, it’s roughly comparable to Krohnkite in terms of features now, but still a very young project, so not as stable yet…
