There is no difference in the way the official viewer and the Cool SL Viewer v1.23.5 render glow (no code change).
Please, verify your graphic settings...
Of course, the Cool SL Viewer v1.19.2 cannot render glows (since it got the legacy (non-Windlight) renderer).
The Cool SL Viewer v1.23.5 can render shadows in the same way as the official viewer v1.23.5, i.e. with a HUGE drop down in the frame rate as well as many graphic quirks (possibly leading to crashes with some GPU and graphic drivers combinations). You obviously need a GPU able to render shadows (Nvidia 8800GT or better, for example).
The procedure to enable shadows is described in
this post.