I can only confirm the Angel Clouds brush presets being faulty through an erroneous installation sequence on your side.
At least if the Angel Clouds - .abr was not imported into Krita as the first “bundle” of this set or combination of two resources, the already named file Angel Clouds - .abr and the Angel_Clouds - Krita .bundle, which has to be installed after the first Angel Clouds - .abr.
But I have to admit, that it is something I discovered myself only short after I published my add-on-bundles.
But okay, import it as the second file now. And now, in Krita’s brush editor select each of the brush presets on the left side after you clicked on the little leftward pointing arrow symbol to display the brush presets, then set the brush size to whatever you want before you click on the little yellow triangle that will show up below the brush presets name on top of the brush editor. After you have gone through all the brush presets and resetted them to their original size and brush tip, that is what clicking the yellow triangle does, a reset of the selected brush’s settings, you should be able using them as intended.
The other bundle Size Flow Brushes doesn’t need this, it is 100% Krita compatible and okay.
Michelist