Sorry for mistake, you are right: dense cloud has 3 200 000 000 points, tie points - 3 900 000
Parameters: 10 deg, max distance 0.3m, cell size 30m. Dense cloud points are located in the area of ~20km2. It is a road that is 35 km long and the buffer is 550 m width.
Update: it took 30 hours to perform a classification in a project with dense cloud 1 300 000 000 points, 10km2, parameters as above.