Use an ordinary wall plug but leave its shoulder level with the face of the tile. The plug will expand into the plasterboard and security of the fixing screw will depend on the bond between the tiles and plasterboard. Since you are fitting light items only this should work fine.
Yes, beethoven using normal rawl plugs flush with a tile will often result in a cracked tile unless the screws are very thin. If the tiles are beefy, you may get away with it.
Generally, if it is only a lightweight thing you are hanging, I normally tap the rawlplug past the tile so it is still in the plasterboard and screw in from there with perhaps a dab of silicone for good measure.
If you must use the tile, use ordinary red plugs with a 6mm drill and no 6 screws, but not near the edge of a tile!
I should clarify my answer. I use fisher wall fixings, these have a sleeve with an internal diameter which for the first 5+mm is a clearance size for the screws being inserted. Expansion therefore only takes place deeper than 5mm or so. This is ideal for the application you describe - the sleeved part stops the screw from direct contact with the tile and all expansion takes place behind the tile.
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