What I did before was rigging the tail using rigify, and then merging the rig with the body rig (the body rig is not a rigify rig).
The tail still mesh still appear some times after that, however when I perform task like undo or changing into other collections, the tail mesh disappear. Strangely, it's still appear on edit mode, and I tried Alt + H too in case I accidentally hiding the mesh but nope, it's still disappear.
Is this a bug with rigify?