SUMMARY
I noticed that the snapping in Krita gets disabled in certain situations.
If it's not a bug, then remember that not all use cases have been considered and so please rework that. I'm making comic pages and good lord, layer styles are
damn resource hungry or not optimized; so I use rectangular vectors with a certain amount of size. The lack of options for image manipulation in Krita hit me hard today. I wanted to move my rectangles and follow a certain layout composition but, unless I use the square handles, snapping to guides won't be enabled, yet I need them to have a fixed size. The arrange functionality is also not intuitive enough so far(they definitely don't cover all use cases or it's because of their lack of support for raster layers, exemple : selecting two or three group of raster/vector layers, and distribute them or align their centers on a vertical or horizontal axis). If you need references, Photoshop is the ultimate father to help you. We may also help for the use cases but they would come from our use of Photoshop. Let us know if we should
open once again a discussion at krita-artists.org...


STEPS TO REPRODUCE
1. have a rectangular vector in one vector layer
2. create a vertical or horizontal guide
3. enable snapping to guide and bounding box(is that even the layer
or group of layer bounds, why does it not support raster layers ?)
4. using the move tool, move the vector layer towards the guide(expect the bounds of the layer to snap with the guide)

OBSERVED RESULT
No snapping at all with the move tool

EXPECTED RESULT
The bounds of the layer or group of layers, whether vector or raster, 
are supposed to snap to the guide when close enough.
If SHIFT was pressed, snapping to the constraints should also be enabled.
It would result in a somewhat complex snapping result, but once handled, it's over. You won't have to think about it for 20 years in the future.

ADDITIONAL INFORMATION : 
Thanks for your hard work which made Krita to reach its 1st place among
Open Source art-making softwares in the world. But we don't want to return to Clip Studio Paint, Inkscape, or Photoshop for certain things that are still missing, it breaks the workflow. 

Thank you for reading this. It's not a mockup or a discussed thread, but it matters a lot.