maybe strange question but is it anyhow possible making a mesh be just light? So if I turn down emission it would just disappear until I crank it up again? Thanks for your attention
You can use the volume material output to make your object pure light :
the emission volume is fast to render (not as smoke).
with very low emission strength :
Be aware that, sometimes, using 0 for strength will make your object black (bug). Use very low values instead.
Use an Add shader to combine a Transparent and an Emission shader.
The inclusion of the Transparent shader (set to 100% white) in this way will result in the mesh being fully transparent regardless of the intensity of the emission. ie, it won't cast a shadow and will be invisible apart from the light it emits.
@lemon kindly provided a comparison of various methods with varying emission :
From left to right...
1) Emission shader only
2) Transparent and Emission combined with Add shader (the one described at the start of this answer)
3) Transparent mixed with Emission
4) Transparent mixed with combined Emission/Transparent
1 and 3 produce shadows (and 1, obviously, turns black so is really not good). 2 and 4 don't produce shadows and are fully transparent - the only difference being that 4 fades at a different rate - mostly due to the Mix factor and the emission strength combining to affect the brightness non-linearly.
For a linearly varying emission with no shadow, number '2' seems the best solution.