About the only document I use is the Q3Map2 Shader Manual - q3map2.robotrenega.../shader_manual/
If I recall correctly, I've heard that GtkRadiant is basically NetRadiant, but with more features. Is it true?
Trenchhroom should be welcomed as an option more, i've seen enough gatekeeping gaslighting on how it's not a 'proper' radiant or whatever. It's certainly more viable than QuArK.
Edited 6.08 minutes after the original posting.