Much the same method as yours.. A geometry-bevelled curve for the glass, with a Solidify modifier to make it a tube. A duplicate of the curve, with a smaller bevel, for the gas.

The glass is just a standard, colourless, almost 0-Roughness, almost 1-Transmission principled BSDF.

The gas uses a the 'Facing' output of a Layer Weight node to make the mask shown on the left, below, to mix between a Transparent and Emission shaders as shown on the right.

..but it still takes a fair bit of tweaking to make it feel 'gaseous'..

Much the same method as yours.. A geometry-bevelled curve for the glass, with a Solidify modifier to make it a tube. A duplicate of the curve, with a smaller bevel, for the gas.

The glass is just a standard, colourless, almost 0-Roughness, almost 1-Transmission principled BSDF.

The gas uses a the 'Facing' output of a Layer Weight node to make the mask shown on the left, below, to mix between a Transparent and Emission shaders as shown on the right.

..but it still takes a fair bit of tweaking to make it feel 'gaseous'..