Assume an Earth-Clone, that has an axial tilt of 90°. How would the circulation of the atmosphere look like? Would there still be three convection cells?
So the axial tilt doesn't actually influence the number of convection cells very much, afaik. It does, however, affect their position. You might also want to note that a world with a 90° axial tilt would essentially present on side to its star half the year and the other half the rest of the year. That means a long day which is summer and a long night which is winter. This leads to some EXTREME weather patterns that until recently were though impossible to overcome (well, at the very least it was thought to be the case for tidally locked planets, but recent simulations show a fast enough spin can compensate that effect). In the case of a 90° planet, the spin will have no effect on spreading the extra heat from the day side though, because the axis faces towards or against the sun for roughly half of the year (and it faces perpendicular the other half). This means that half of the year, you'd have heat trapped in the day cycle either on one side or the other depending if you take the winter or summer quarter. This could be mitigated if you have a short enough year but then you'd run into problems of star size with instability that features coronal ejections and lethal rays so… maybe not a good idea (red dwarves are extremely unstable).
What would affect the number of cells is the rotation speed.