If the transformer is Electronic Low-Voltage then you typically derate the dimmer 50%. This goes for wallbox dimmers or dimming modules.

Keeping that in mind a dimmer specifically listed for Electronic Low-Voltage is generally a standard dimmer derated 50% and priced at a premium. Some low voltage dimmers simply don't like dimming and will respond irradically to amy dimmer.

As for neon, read the power supply. Neon is more like fluorescent so dimming may be a challenge.