If your kitops insert simply makes a hole that just breaks up the surface, letting you peek inside the mesh, You will probably need to change the boolean mode from fast -> exact / move the insert slightly up on the local Z axis.

Decalmachine decals work differently in 2.93 and 3.0, due to the new changes to the principled shader node. If you downloaded the 2.93 decal pack then you can safely use it in 2.93, but for 3.0 you will have to either convert it automatically using decalmachine in the addons tab, or just download the pre-converted 3.0 decal pack from the download page.