There are three ways to get power to work an electronic switch.
1) A neutral connection as well as line in and out.
2) A battery
3) To pass a small amount of current through the item being switched, even when off.
So many bulbs have a bleed resistor or capacitor, so a small amount of current will not light the bulb, but there are no rules as to how much, since working with AC there is likely some inductive and capacitive linking anyway, this will increase with two-way switching, as we run live wires alongside the switch line, so all bulbs to work with AC will allow a little current without lighting, but down to how much.
These bulbs
are G9 the small one will fit inside the cover used with the halogen, but there is not the room inside the bulb to have smoothing capacitors and leak resistors, and with electronic switches tend to stay on dim when switched off, and have a shimmer when on, the larger one has the room, but will not fit inside the covers.
For on/off switching, the Tapo TP-Link switches use a battery, so will work with no shimmer, or staying on dim, batteries last around a year, and can be changed without removing the whole switch. So as far as I am aware, they are the only battery powered, using a relay is the other method where no neutral at the switch, Sonoff are popular and relay fitted in the lamp where you do have a neutral.
To dim lights best is smart bulb, as it allows one to change colour temperature as well, even the colour of the light, but dimming switches really only work with large bulbs, which are big enough to house the capacitors etc, needed to stop the shimmer.
