I assume, the main problem in this parameter isn't noise - I don't see noise at all - it is aliasing ( the
stairieness within the "side-pillows" and elsewhere). Noise means some grainieness. The aliasing seems to be a property of the used formula combination. You can reduce this by antialiasing a downscaled bigger render. The max useful ratio here is 1:3. I attached a parameter with increased raystep and stepwith values, that should do and a 1:3 scaling for a destination res of 960 x 576. Hope that helps.
Mandelbulb3Dv18{
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...................1./........xDaNaNaNaNaz1.....................................
................................................................................
.....................2.....3....6....2IPVdLOiR46HJbQa/..........................
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................................}
{Titel: maybe23}