Why glow looks weaker on Roblox

A Roblox part has no brightness channel. It has one glowing material, Neon, which is whole part, unlit and has no intensity setting. So glow is approximated on Roblox and faithful everywhere else. This is the documented trade, not a bug to work around.

What the export does with it: the part's colour is tinted toward your emissive colour, and at intensity 0.5 or above the part becomes Neon.

Glass never becomes Neon, whatever the intensity. Neon is unlit, so it erases the shading that makes a facet read as glass. If you want something transmissive and blazing, build it as two objects: a glass shell around an opaque glowing core.

Emissive only exists on the lit material types, which are Standard, Phong, Toon and Glass. Basic, Wireframe and Neon have no emissive channel at all, in any target, and the rows disappear when you pick one.

Godot and glTF carry emissive properly, so a model exported to Godot glows the way the viewport does.