<<<<Considering that I don't need the GPU to process massive scientific calculation (FP64) but only for visualization, 3d modelling, 3d rendering and
2d Gpu Painting, can I get rid of FP64 performance and go for a ultra powerful FP32 (11 TFplos) Gtx Nvidia 1080 Ti ?>>>>

Answer : YES! Go Marco Go!
(or wait for the next GTX1090TiXNewUltraMega++ )
\:^P